837 lines
31 KiB
Rust
837 lines
31 KiB
Rust
use bit_vec::BitVec;
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use byteorder::{BigEndian, WriteBytesExt};
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use colors::{AlphaOptim, BitDepth, ColorType};
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use crc::crc32;
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use deflate;
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use error::PngError;
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use filters::*;
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use headers::*;
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use interlace::{deinterlace_image, interlace_image};
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use itertools::{flatten, Itertools};
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use reduction::bit_depth::*;
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use reduction::color::*;
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use std::collections::{HashMap, HashSet};
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use std::fs::File;
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use std::io::{Read, Seek, SeekFrom};
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use std::iter::Iterator;
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use std::path::Path;
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#[cfg(feature = "parallel")]
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use rayon::prelude::*;
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use atomicmin::AtomicMin;
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const STD_COMPRESSION: u8 = 8;
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const STD_STRATEGY: u8 = 2; // Huffman only
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const STD_WINDOW: u8 = 15;
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const STD_FILTERS: [u8; 2] = [0, 5];
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mod scan_lines;
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use self::scan_lines::{ScanLine, ScanLines};
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#[derive(Debug, Clone)]
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/// Contains all data relevant to a PNG image
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pub struct PngData {
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/// The filtered and compressed data of the IDAT chunk
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pub idat_data: Vec<u8>,
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/// The headers stored in the IHDR chunk
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pub ihdr_data: IhdrData,
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/// The uncompressed, optionally filtered data from the IDAT chunk
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pub raw_data: Vec<u8>,
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/// The palette containing colors used in an Indexed image
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/// Contains 3 bytes per color (R+G+B), up to 768
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pub palette: Option<Vec<u8>>,
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/// The pixel value that should be rendered as transparent
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pub transparency_pixel: Option<Vec<u8>>,
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/// A map of how transparent each color in the palette should be
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pub transparency_palette: Option<Vec<u8>>,
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/// All non-critical headers from the PNG are stored here
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pub aux_headers: HashMap<String, Vec<u8>>,
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}
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impl PngData {
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/// Create a new `PngData` struct by opening a file
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#[inline]
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pub fn new(filepath: &Path, fix_errors: bool) -> Result<PngData, PngError> {
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let byte_data = PngData::read_file(filepath)?;
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PngData::from_slice(&byte_data, fix_errors)
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}
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pub fn read_file(filepath: &Path) -> Result<Vec<u8>, PngError> {
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let mut file = match File::open(filepath) {
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Ok(f) => f,
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Err(_) => return Err(PngError::new("Failed to open file for reading")),
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};
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// Check file for PNG header
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let mut header = [0; 8];
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if file.read_exact(&mut header).is_err() {
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return Err(PngError::new("Not a PNG file: too small"));
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}
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if !file_header_is_valid(&header) {
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return Err(PngError::new("Invalid PNG header detected"));
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}
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if file.seek(SeekFrom::Start(0)).is_err() {
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return Err(PngError::new("Failed to read from file"));
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}
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// Read raw png data into memory
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let mut byte_data: Vec<u8> =
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Vec::with_capacity(file.metadata().map(|m| m.len() as usize).unwrap_or(0));
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match file.read_to_end(&mut byte_data) {
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Ok(_) => (),
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Err(_) => return Err(PngError::new("Failed to read from file")),
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}
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Ok(byte_data)
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}
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/// Create a new `PngData` struct by reading a slice
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pub fn from_slice(byte_data: &[u8], fix_errors: bool) -> Result<PngData, PngError> {
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let mut byte_offset: usize = 0;
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// Test that png header is valid
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let header: Vec<u8> = byte_data.iter().take(8).cloned().collect();
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if !file_header_is_valid(header.as_ref()) {
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return Err(PngError::new("Invalid PNG header detected"));
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}
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byte_offset += 8;
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// Read the data headers
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let mut aux_headers: HashMap<String, Vec<u8>> = HashMap::new();
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let mut idat_headers: Vec<u8> = Vec::new();
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loop {
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let header = parse_next_header(byte_data, &mut byte_offset, fix_errors);
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let header = match header {
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Ok(x) => x,
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Err(x) => return Err(x),
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};
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let header = match header {
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Some(x) => x,
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None => break,
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};
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if header.0 == "IDAT" {
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idat_headers.extend(header.1);
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} else if header.0 == "acTL" {
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return Err(PngError::new("APNG files are not (yet) supported"));
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} else {
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aux_headers.insert(header.0, header.1);
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}
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}
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// Parse the headers into our PngData
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if idat_headers.is_empty() {
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return Err(PngError::new("Image data was empty, skipping"));
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}
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if aux_headers.get("IHDR").is_none() {
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return Err(PngError::new("Image header data was missing, skipping"));
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}
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let ihdr_header = match parse_ihdr_header(aux_headers.remove("IHDR").unwrap().as_ref()) {
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Ok(x) => x,
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Err(x) => return Err(x),
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};
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let raw_data = match deflate::inflate(idat_headers.as_ref()) {
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Ok(x) => x,
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Err(x) => return Err(x),
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};
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// Handle transparency header
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let mut has_transparency_pixel = false;
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let mut has_transparency_palette = false;
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if aux_headers.contains_key("tRNS") {
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if ihdr_header.color_type == ColorType::Indexed {
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has_transparency_palette = true;
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} else {
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has_transparency_pixel = true;
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}
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}
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let mut png_data = PngData {
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idat_data: idat_headers,
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ihdr_data: ihdr_header,
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raw_data,
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palette: aux_headers.remove("PLTE"),
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transparency_pixel: if has_transparency_pixel {
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aux_headers.remove("tRNS")
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} else {
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None
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},
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transparency_palette: if has_transparency_palette {
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aux_headers.remove("tRNS")
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} else {
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None
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},
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aux_headers,
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};
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png_data.raw_data = png_data.unfilter_image();
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// Return the PngData
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Ok(png_data)
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}
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#[doc(hidden)]
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pub fn reset_from_original(&mut self, original: &PngData) {
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self.idat_data = original.idat_data.clone();
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self.ihdr_data = original.ihdr_data;
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self.raw_data = original.raw_data.clone();
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self.palette = original.palette.clone();
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self.transparency_pixel = original.transparency_pixel.clone();
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self.transparency_palette = original.transparency_palette.clone();
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self.aux_headers = original.aux_headers.clone();
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}
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/// Return the number of channels in the image, based on color type
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#[inline]
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pub fn channels_per_pixel(&self) -> u8 {
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self.ihdr_data.color_type.channels_per_pixel()
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}
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/// Format the `PngData` struct into a valid PNG bytestream
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pub fn output(&self) -> Vec<u8> {
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// PNG header
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let mut output = vec![0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
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// IHDR
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let mut ihdr_data = Vec::with_capacity(13);
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let _ = ihdr_data.write_u32::<BigEndian>(self.ihdr_data.width);
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let _ = ihdr_data.write_u32::<BigEndian>(self.ihdr_data.height);
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let _ = ihdr_data.write_u8(self.ihdr_data.bit_depth.as_u8());
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let _ = ihdr_data.write_u8(self.ihdr_data.color_type.png_header_code());
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let _ = ihdr_data.write_u8(0); // Compression -- deflate
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let _ = ihdr_data.write_u8(0); // Filter method -- 5-way adaptive filtering
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let _ = ihdr_data.write_u8(self.ihdr_data.interlaced);
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write_png_block(b"IHDR", &ihdr_data, &mut output);
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// Ancillary headers
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for (key, header) in self.aux_headers
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.iter()
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.filter(|&(key, _)| !(*key == "bKGD" || *key == "hIST" || *key == "tRNS"))
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{
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write_png_block(key.as_bytes(), header, &mut output);
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}
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// Palette
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if let Some(ref palette) = self.palette {
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write_png_block(b"PLTE", palette, &mut output);
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if let Some(ref transparency_palette) = self.transparency_palette {
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// Transparency pixel
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write_png_block(b"tRNS", transparency_palette, &mut output);
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}
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} else if let Some(ref transparency_pixel) = self.transparency_pixel {
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// Transparency pixel
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write_png_block(b"tRNS", transparency_pixel, &mut output);
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}
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// Special ancillary headers that need to come after PLTE but before IDAT
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for (key, header) in self.aux_headers
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.iter()
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.filter(|&(key, _)| *key == "bKGD" || *key == "hIST" || *key == "tRNS")
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{
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write_png_block(key.as_bytes(), header, &mut output);
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}
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// IDAT data
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write_png_block(b"IDAT", &self.idat_data, &mut output);
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// Stream end
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write_png_block(b"IEND", &[], &mut output);
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output
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}
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/// Return an iterator over the scanlines of the image
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#[inline]
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pub fn scan_lines(&self) -> ScanLines {
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ScanLines {
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png: self,
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start: 0,
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end: 0,
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pass: None,
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}
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}
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/// Reverse all filters applied on the image, returning an unfiltered IDAT bytestream
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pub fn unfilter_image(&self) -> Vec<u8> {
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let mut unfiltered = Vec::with_capacity(self.raw_data.len());
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let bpp = ((f32::from(self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel())) / 8f32)
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.ceil() as usize;
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let mut last_line: Vec<u8> = Vec::new();
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let mut last_pass = 1;
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for line in self.scan_lines() {
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if let Some(pass) = line.pass {
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if pass != last_pass {
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last_line = Vec::new();
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last_pass = pass;
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}
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}
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let unfiltered_line = unfilter_line(line.filter, bpp, &line.data, &last_line);
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unfiltered.push(0);
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unfiltered.extend_from_slice(&unfiltered_line);
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last_line = unfiltered_line;
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}
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unfiltered
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}
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/// Apply the specified filter type to all rows in the image
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/// 0: None
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/// 1: Sub
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/// 2: Up
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/// 3: Average
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/// 4: Paeth
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/// 5: All (heuristically pick the best filter for each line)
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pub fn filter_image(&self, filter: u8) -> Vec<u8> {
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let mut filtered = Vec::with_capacity(self.raw_data.len());
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let bpp = ((f32::from(self.ihdr_data.bit_depth.as_u8() * self.channels_per_pixel())) / 8f32)
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.ceil() as usize;
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let mut last_line: Vec<u8> = Vec::new();
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let mut last_pass: Option<u8> = None;
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for line in self.scan_lines() {
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match filter {
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0 | 1 | 2 | 3 | 4 => {
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let filter = if last_pass == line.pass || filter <= 1 {
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filter
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} else {
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0
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};
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filtered.push(filter);
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filtered.extend_from_slice(&filter_line(filter, bpp, &line.data, &last_line));
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}
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5 => {
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// Heuristically guess best filter per line
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// Uses MSAD algorithm mentioned in libpng reference docs
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// http://www.libpng.org/pub/png/book/chapter09.html
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let mut trials: HashMap<u8, Vec<u8>> = HashMap::with_capacity(5);
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// Avoid vertical filtering on first line of each interlacing pass
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for filter in if last_pass == line.pass { 0..5 } else { 0..2 } {
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trials.insert(filter, filter_line(filter, bpp, &line.data, &last_line));
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}
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let (best_filter, best_line) = trials
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.iter()
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.min_by_key(|x| {
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x.1.iter().fold(0u64, |acc, &x| {
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let signed = x as i8;
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acc + i16::from(signed).abs() as u64
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})
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})
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.unwrap();
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filtered.push(*best_filter);
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filtered.extend_from_slice(best_line);
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}
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_ => unreachable!(),
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}
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last_line = line.data;
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last_pass = line.pass;
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}
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filtered
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}
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/// Attempt to reduce the bit depth of the image
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/// Returns true if the bit depth was reduced, false otherwise
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pub fn reduce_bit_depth(&mut self) -> bool {
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if self.ihdr_data.bit_depth != BitDepth::Sixteen {
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if self.ihdr_data.color_type == ColorType::Indexed
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|| self.ihdr_data.color_type == ColorType::Grayscale
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{
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return reduce_bit_depth_8_or_less(self);
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}
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return false;
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}
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// Reduce from 16 to 8 bits per channel per pixel
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let mut reduced = Vec::with_capacity(
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(self.ihdr_data.width * self.ihdr_data.height * u32::from(self.channels_per_pixel())
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+ self.ihdr_data.height) as usize,
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);
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let mut high_byte = 0;
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for line in self.scan_lines() {
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reduced.push(line.filter);
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for (i, byte) in line.data.iter().enumerate() {
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if i % 2 == 0 {
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// High byte
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high_byte = *byte;
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} else {
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// Low byte
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if high_byte != *byte {
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// Can't reduce, exit early
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return false;
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}
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reduced.push(*byte);
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}
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}
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}
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self.ihdr_data.bit_depth = BitDepth::Eight;
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self.raw_data = reduced;
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true
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}
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/// Attempt to reduce the number of colors in the palette
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/// Returns true if the palette was reduced, false otherwise
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pub fn reduce_palette(&mut self) -> bool {
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if self.ihdr_data.color_type != ColorType::Indexed {
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// Can't reduce if there is no palette
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return false;
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}
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if self.ihdr_data.bit_depth == BitDepth::One {
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// Gains from 1-bit images will be at most 1 byte
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// Not worth the CPU time
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return false;
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}
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// A palette with RGB or RGBA slices
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let palette = if let Some(ref trns) = self.transparency_palette {
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self.palette
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.clone()
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.unwrap()
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.chunks(3)
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.zip(trns.iter().chain([255].iter().cycle()))
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.flat_map(|(pixel, trns)| {
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let mut pixel = pixel.to_owned();
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pixel.push(*trns);
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pixel
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})
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.collect()
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} else {
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self.palette.clone().unwrap()
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};
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let mut indexed_palette: Vec<&[u8]> = palette
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.chunks(if self.transparency_palette.is_some() {
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4
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} else {
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3
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})
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.collect();
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// A map of old indexes to new ones, for any moved
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let mut index_map: HashMap<u8, u8> = HashMap::new();
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// A list of (original) indices that are duplicates and no longer needed
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let mut duplicates: Vec<u8> = Vec::new();
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{
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// Find duplicate entries in the palette
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let mut seen: HashMap<&[u8], u8> = HashMap::with_capacity(indexed_palette.len());
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for (i, color) in indexed_palette.iter().enumerate() {
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if seen.contains_key(color) {
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let index = &seen[color];
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duplicates.push(i as u8);
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index_map.insert(i as u8, *index);
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} else {
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seen.insert(*color, i as u8);
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}
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}
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}
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// Remove duplicates from the data
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if !duplicates.is_empty() {
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self.do_palette_reduction(&duplicates, &mut index_map, &mut indexed_palette);
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}
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// Find palette entries that are never used
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let mut seen = HashSet::with_capacity(indexed_palette.len());
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for line in self.scan_lines() {
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match self.ihdr_data.bit_depth {
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BitDepth::Eight => for byte in &line.data {
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seen.insert(*byte);
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},
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BitDepth::Four => {
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let bitvec = BitVec::from_bytes(&line.data);
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let mut current = 0u8;
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for (i, bit) in bitvec.iter().enumerate() {
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let mod_i = i % 4;
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if bit {
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current += 1u8 << (3 - mod_i);
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}
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if mod_i == 3 {
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seen.insert(current);
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current = 0;
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}
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}
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}
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BitDepth::Two => {
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let bitvec = BitVec::from_bytes(&line.data);
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let mut current = 0u8;
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for (i, bit) in bitvec.iter().enumerate() {
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let mod_i = i % 2;
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if bit {
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current += 1u8 << (1 - mod_i);
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}
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if mod_i == 1 {
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seen.insert(current);
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current = 0;
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}
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}
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}
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_ => unreachable!(),
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}
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if seen.len() == indexed_palette.len() {
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// Exit early if no further possible optimizations
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// Check at the end of each line
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// Checking after every pixel would be overly expensive
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return !duplicates.is_empty();
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}
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}
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let unused: Vec<u8> = (0..indexed_palette.len() as u8)
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.filter(|i| !seen.contains(i))
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.collect();
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|
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// Remove unused palette indices
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self.do_palette_reduction(&unused, &mut index_map, &mut indexed_palette);
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|
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true
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}
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|
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fn do_palette_reduction(
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&mut self,
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indices_to_remove: &[u8],
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index_map: &mut HashMap<u8, u8>,
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indexed_palette: &mut Vec<&[u8]>,
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) {
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let mut new_data = Vec::with_capacity(self.raw_data.len());
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let original_len = indexed_palette.len();
|
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for idx in indices_to_remove.iter().sorted_by(|a, b| b.cmp(a)) {
|
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for i in (*idx as usize + 1)..original_len {
|
|
let existing = index_map.entry(i as u8).or_insert(i as u8);
|
|
if *existing >= *idx {
|
|
*existing -= 1;
|
|
}
|
|
}
|
|
indexed_palette.remove(*idx as usize);
|
|
if let Some(ref mut alpha) = self.transparency_palette {
|
|
if (*idx as usize) < alpha.len() {
|
|
alpha.remove(*idx as usize);
|
|
}
|
|
}
|
|
}
|
|
if let Some(ref mut alpha) = self.transparency_palette {
|
|
while let Some(255) = alpha.last().cloned() {
|
|
alpha.pop();
|
|
}
|
|
}
|
|
// Reassign data bytes to new indices
|
|
for line in self.scan_lines() {
|
|
new_data.push(line.filter);
|
|
match self.ihdr_data.bit_depth {
|
|
BitDepth::Eight => for byte in &line.data {
|
|
if let Some(new_idx) = index_map.get(byte) {
|
|
new_data.push(*new_idx);
|
|
} else {
|
|
new_data.push(*byte);
|
|
}
|
|
},
|
|
BitDepth::Four => for byte in &line.data {
|
|
let upper = *byte & 0b1111_0000;
|
|
let lower = *byte & 0b0000_1111;
|
|
let mut new_byte = 0u8;
|
|
new_byte |= if let Some(new_idx) = index_map.get(&(upper >> 4)) {
|
|
*new_idx << 4
|
|
} else {
|
|
upper
|
|
};
|
|
new_byte |= if let Some(new_idx) = index_map.get(&lower) {
|
|
*new_idx
|
|
} else {
|
|
lower
|
|
};
|
|
new_data.push(new_byte);
|
|
},
|
|
BitDepth::Two => for byte in &line.data {
|
|
let one = *byte & 0b1100_0000;
|
|
let two = *byte & 0b0011_0000;
|
|
let three = *byte & 0b0000_1100;
|
|
let four = *byte & 0b0000_0011;
|
|
let mut new_byte = 0u8;
|
|
new_byte |= if let Some(new_idx) = index_map.get(&(one >> 6)) {
|
|
*new_idx << 6
|
|
} else {
|
|
one
|
|
};
|
|
new_byte |= if let Some(new_idx) = index_map.get(&(two >> 4)) {
|
|
*new_idx << 4
|
|
} else {
|
|
two
|
|
};
|
|
new_byte |= if let Some(new_idx) = index_map.get(&(three >> 2)) {
|
|
*new_idx << 2
|
|
} else {
|
|
three
|
|
};
|
|
new_byte |= if let Some(new_idx) = index_map.get(&four) {
|
|
*new_idx
|
|
} else {
|
|
four
|
|
};
|
|
new_data.push(new_byte);
|
|
},
|
|
_ => unreachable!(),
|
|
}
|
|
}
|
|
index_map.clear();
|
|
self.raw_data = new_data;
|
|
let new_palette = flatten(indexed_palette.iter().cloned())
|
|
.enumerate()
|
|
.filter(|&(i, _)| !(self.transparency_palette.is_some() && i % 4 == 3))
|
|
.map(|(_, x)| *x)
|
|
.collect::<Vec<u8>>();
|
|
self.palette = Some(new_palette);
|
|
}
|
|
|
|
/// Attempt to reduce the color type of the image
|
|
/// Returns true if the color type was reduced, false otherwise
|
|
pub fn reduce_color_type(&mut self) -> bool {
|
|
let mut changed = false;
|
|
let mut should_reduce_bit_depth = false;
|
|
|
|
// Go down one step at a time
|
|
// Maybe not the most efficient, but it's safe
|
|
if self.ihdr_data.color_type == ColorType::RGBA {
|
|
if reduce_rgba_to_grayscale_alpha(self) || reduce_rgba_to_rgb(self) {
|
|
changed = true;
|
|
} else if reduce_rgba_to_palette(self) {
|
|
changed = true;
|
|
should_reduce_bit_depth = true;
|
|
}
|
|
}
|
|
|
|
if self.ihdr_data.color_type == ColorType::GrayscaleAlpha
|
|
&& reduce_grayscale_alpha_to_grayscale(self)
|
|
{
|
|
changed = true;
|
|
should_reduce_bit_depth = true;
|
|
}
|
|
|
|
if self.ihdr_data.color_type == ColorType::RGB
|
|
&& (reduce_rgb_to_grayscale(self) || reduce_rgb_to_palette(self))
|
|
{
|
|
changed = true;
|
|
should_reduce_bit_depth = true;
|
|
}
|
|
|
|
if should_reduce_bit_depth {
|
|
// Some conversions will allow us to perform bit depth reduction that
|
|
// wasn't possible before
|
|
reduce_bit_depth_8_or_less(self);
|
|
}
|
|
|
|
changed
|
|
}
|
|
|
|
pub fn try_alpha_reduction(&mut self, alphas: &HashSet<AlphaOptim>) {
|
|
assert!(!alphas.is_empty());
|
|
let alphas = alphas.iter().collect::<Vec<_>>();
|
|
let best_size = AtomicMin::new(None);
|
|
#[cfg(feature = "parallel")]
|
|
let alphas_iter = alphas.par_iter().with_max_len(1);
|
|
#[cfg(not(feature = "parallel"))]
|
|
let alphas_iter = alphas.iter();
|
|
let best = alphas_iter
|
|
.filter_map(|&alpha| {
|
|
let mut image = self.clone();
|
|
image.reduce_alpha_channel(*alpha);
|
|
#[cfg(feature = "parallel")]
|
|
let filters_iter = STD_FILTERS.par_iter().with_max_len(1);
|
|
#[cfg(not(feature = "parallel"))]
|
|
let filters_iter = STD_FILTERS.iter();
|
|
filters_iter
|
|
.filter_map(|f| {
|
|
deflate::deflate(
|
|
&image.filter_image(*f),
|
|
STD_COMPRESSION,
|
|
STD_STRATEGY,
|
|
STD_WINDOW,
|
|
&best_size,
|
|
).ok()
|
|
.as_ref().map(|l| {
|
|
best_size.set_min(l.len());
|
|
l.len()
|
|
})
|
|
})
|
|
.min()
|
|
.map(|size| (size, image))
|
|
})
|
|
.min_by_key(|&(size, _)| size);
|
|
|
|
if let Some(best) = best {
|
|
self.raw_data = best.1.raw_data;
|
|
}
|
|
}
|
|
|
|
pub fn reduce_alpha_channel(&mut self, optim: AlphaOptim) -> bool {
|
|
let (bpc, bpp) = match self.ihdr_data.color_type {
|
|
ColorType::RGBA | ColorType::GrayscaleAlpha => {
|
|
let cpp = self.channels_per_pixel();
|
|
let bpc = self.ihdr_data.bit_depth.as_u8() / 8;
|
|
(bpc as usize, (bpc * cpp) as usize)
|
|
}
|
|
_ => {
|
|
return false;
|
|
}
|
|
};
|
|
|
|
match optim {
|
|
AlphaOptim::NoOp => {
|
|
return false;
|
|
}
|
|
AlphaOptim::Black => {
|
|
self.raw_data = self.reduce_alpha_to_black(bpc, bpp);
|
|
}
|
|
AlphaOptim::White => {
|
|
self.raw_data = self.reduce_alpha_to_white(bpc, bpp);
|
|
}
|
|
AlphaOptim::Up => {
|
|
self.raw_data = self.reduce_alpha_to_up(bpc, bpp);
|
|
}
|
|
AlphaOptim::Down => {
|
|
self.raw_data = self.reduce_alpha_to_down(bpc, bpp);
|
|
}
|
|
AlphaOptim::Left => {
|
|
self.raw_data = self.reduce_alpha_to_left(bpc, bpp);
|
|
}
|
|
AlphaOptim::Right => {
|
|
self.raw_data = self.reduce_alpha_to_right(bpc, bpp);
|
|
}
|
|
}
|
|
|
|
true
|
|
}
|
|
|
|
fn reduce_alpha_to_black(&self, bpc: usize, bpp: usize) -> Vec<u8> {
|
|
let mut reduced = Vec::with_capacity(self.raw_data.len());
|
|
for line in self.scan_lines() {
|
|
reduced.push(line.filter);
|
|
for pixel in line.data.chunks(bpp) {
|
|
if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
|
|
for _ in 0..bpp {
|
|
reduced.push(0);
|
|
}
|
|
} else {
|
|
reduced.extend_from_slice(pixel);
|
|
}
|
|
}
|
|
}
|
|
reduced
|
|
}
|
|
|
|
fn reduce_alpha_to_white(&self, bpc: usize, bpp: usize) -> Vec<u8> {
|
|
let mut reduced = Vec::with_capacity(self.raw_data.len());
|
|
for line in self.scan_lines() {
|
|
reduced.push(line.filter);
|
|
for pixel in line.data.chunks(bpp) {
|
|
if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
|
|
for _ in 0..(bpp - bpc) {
|
|
reduced.push(255);
|
|
}
|
|
for _ in 0..bpc {
|
|
reduced.push(0);
|
|
}
|
|
} else {
|
|
reduced.extend_from_slice(pixel);
|
|
}
|
|
}
|
|
}
|
|
reduced
|
|
}
|
|
|
|
fn reduce_alpha_to_up(&self, bpc: usize, bpp: usize) -> Vec<u8> {
|
|
let mut lines = Vec::new();
|
|
let scan_lines = self.scan_lines().collect::<Vec<ScanLine>>();
|
|
let mut last_line = vec![0; scan_lines[0].data.len()];
|
|
let mut current_line = Vec::with_capacity(last_line.len());
|
|
for line in scan_lines.into_iter().rev() {
|
|
current_line.push(line.filter);
|
|
for (pixel, last_pixel) in line.data.chunks(bpp).zip(last_line.chunks(bpp)) {
|
|
if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
|
|
current_line.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
|
|
for _ in 0..bpc {
|
|
current_line.push(0);
|
|
}
|
|
} else {
|
|
current_line.extend_from_slice(pixel);
|
|
}
|
|
}
|
|
last_line = current_line.clone();
|
|
lines.push(current_line.clone());
|
|
current_line.clear();
|
|
}
|
|
flatten(lines.into_iter().rev()).collect()
|
|
}
|
|
|
|
fn reduce_alpha_to_down(&self, bpc: usize, bpp: usize) -> Vec<u8> {
|
|
let mut reduced = Vec::with_capacity(self.raw_data.len());
|
|
let mut last_line = vec![0; self.scan_lines().next().unwrap().data.len()];
|
|
for line in self.scan_lines() {
|
|
reduced.push(line.filter);
|
|
for (pixel, last_pixel) in line.data.chunks(bpp).zip(last_line.chunks(bpp)) {
|
|
if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
|
|
reduced.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
|
|
for _ in 0..bpc {
|
|
reduced.push(0);
|
|
}
|
|
} else {
|
|
reduced.extend_from_slice(pixel);
|
|
}
|
|
}
|
|
last_line = reduced.clone();
|
|
}
|
|
reduced
|
|
}
|
|
|
|
fn reduce_alpha_to_left(&self, bpc: usize, bpp: usize) -> Vec<u8> {
|
|
let mut reduced = Vec::with_capacity(self.raw_data.len());
|
|
for line in self.scan_lines() {
|
|
let mut line_bytes = Vec::with_capacity(line.data.len());
|
|
let mut last_pixel = vec![0; bpp];
|
|
for pixel in line.data.chunks(bpp).rev() {
|
|
if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
|
|
line_bytes.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
|
|
for _ in 0..bpc {
|
|
line_bytes.push(0);
|
|
}
|
|
} else {
|
|
line_bytes.extend_from_slice(pixel);
|
|
}
|
|
last_pixel = pixel.to_owned();
|
|
}
|
|
reduced.push(line.filter);
|
|
reduced.extend(flatten(line_bytes.chunks(bpp).rev()));
|
|
}
|
|
reduced
|
|
}
|
|
|
|
fn reduce_alpha_to_right(&self, bpc: usize, bpp: usize) -> Vec<u8> {
|
|
let mut reduced = Vec::with_capacity(self.raw_data.len());
|
|
for line in self.scan_lines() {
|
|
reduced.push(line.filter);
|
|
let mut last_pixel = vec![0; bpp];
|
|
for pixel in line.data.chunks(bpp) {
|
|
if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
|
|
reduced.extend_from_slice(&last_pixel[0..(bpp - bpc)]);
|
|
for _ in 0..bpc {
|
|
reduced.push(0);
|
|
}
|
|
} else {
|
|
reduced.extend_from_slice(pixel);
|
|
}
|
|
last_pixel = pixel.to_owned();
|
|
}
|
|
}
|
|
reduced
|
|
}
|
|
|
|
/// Convert the image to the specified interlacing type
|
|
/// Returns true if the interlacing was changed, false otherwise
|
|
/// The `interlace` parameter specifies the *new* interlacing mode
|
|
/// Assumes that the data has already been de-filtered
|
|
#[inline]
|
|
pub fn change_interlacing(&mut self, interlace: u8) -> bool {
|
|
if interlace == self.ihdr_data.interlaced {
|
|
return false;
|
|
}
|
|
|
|
if interlace == 1 {
|
|
// Convert progressive to interlaced data
|
|
interlace_image(self);
|
|
} else {
|
|
// Convert interlaced to progressive data
|
|
deinterlace_image(self);
|
|
}
|
|
true
|
|
}
|
|
}
|
|
|
|
fn write_png_block(key: &[u8], header: &[u8], output: &mut Vec<u8>) {
|
|
let mut header_data = Vec::with_capacity(header.len() + 4);
|
|
header_data.extend_from_slice(key);
|
|
header_data.extend_from_slice(header);
|
|
output.reserve(header_data.len() + 8);
|
|
let _ = output.write_u32::<BigEndian>(header_data.len() as u32 - 4);
|
|
let crc = crc32::checksum_ieee(&header_data);
|
|
output.append(&mut header_data);
|
|
let _ = output.write_u32::<BigEndian>(crc);
|
|
}
|