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Remove FIXME sections from code

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One section can't be improved from what I can gather,
because we have to iterate the number of bits per pixel in advance.

The output section has been refactored to pull the block writing code
into a separate function.

Fixes #19
This commit is contained in:
Joshua Holmer 2016-03-21 12:14:22 -04:00
parent aec8e412a3
commit 85ea2c21e5
1 changed files with 20 additions and 63 deletions
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83
src/png.rs
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@ -290,12 +290,10 @@ impl PngData {
}
/// Format the `PngData` struct into a valid PNG bytestream
pub fn output(&self) -> Vec<u8> {
// FIXME: This code can all be refactored
// PNG header
let mut output = vec![0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
// IHDR
let mut ihdr_data = Vec::with_capacity(17);
ihdr_data.extend_from_slice(b"IHDR");
let mut ihdr_data = Vec::with_capacity(13);
ihdr_data.write_u32::<BigEndian>(self.ihdr_data.width).ok();
ihdr_data.write_u32::<BigEndian>(self.ihdr_data.height).ok();
ihdr_data.write_u8(self.ihdr_data.bit_depth.as_u8()).ok();
@ -303,85 +301,34 @@ impl PngData {
ihdr_data.write_u8(0).ok(); // Compression -- deflate
ihdr_data.write_u8(0).ok(); // Filter method -- 5-way adaptive filtering
ihdr_data.write_u8(self.ihdr_data.interlaced).ok();
output.reserve(ihdr_data.len() + 8);
output.write_u32::<BigEndian>(ihdr_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&ihdr_data);
output.append(&mut ihdr_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(b"IHDR", &ihdr_data, &mut output);
// Ancillary headers
for (key, header) in self.aux_headers.iter().filter(|&(ref key, _)| {
!(**key == "bKGD" || **key == "hIST" || **key == "tRNS")
}) {
let mut header_data = Vec::with_capacity(header.len() + 4);
header_data.extend(key.as_bytes());
header_data.extend_from_slice(header);
output.reserve(header_data.len() + 8);
output.write_u32::<BigEndian>(header_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&header_data);
output.append(&mut header_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(&key.as_bytes(), &header, &mut output);
}
// Palette
if let Some(palette) = self.palette.clone() {
let mut palette_data = Vec::with_capacity(palette.len() + 4);
palette_data.extend_from_slice(b"PLTE");
palette_data.extend(palette);
output.reserve(palette_data.len() + 8);
output.write_u32::<BigEndian>(palette_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&palette_data);
output.append(&mut palette_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(b"PLTE", &palette, &mut output);
if let Some(transparency_palette) = self.transparency_palette.clone() {
// Transparency pixel
let mut palette_data = Vec::with_capacity(transparency_palette.len() + 4);
palette_data.extend_from_slice(b"tRNS");
palette_data.extend(transparency_palette);
output.reserve(palette_data.len() + 8);
output.write_u32::<BigEndian>(palette_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&palette_data);
output.append(&mut palette_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(b"tRNS", &transparency_palette, &mut output);
}
} else if let Some(transparency_pixel) = self.transparency_pixel.clone() {
// Transparency pixel
let mut pixel_data = Vec::with_capacity(transparency_pixel.len() + 4);
pixel_data.extend_from_slice(b"tRNS");
pixel_data.extend(transparency_pixel);
output.reserve(pixel_data.len() + 8);
output.write_u32::<BigEndian>(pixel_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&pixel_data);
output.append(&mut pixel_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(b"tRNS", &transparency_pixel, &mut output);
}
// Special ancillary headers that need to come after PLTE but before IDAT
for (key, header) in self.aux_headers.iter().filter(|&(ref key, _)| {
**key == "bKGD" || **key == "hIST" || **key == "tRNS"
}) {
let mut header_data = Vec::with_capacity(header.len() + 4);
header_data.extend(key.as_bytes());
header_data.extend_from_slice(header);
output.reserve(header_data.len() + 8);
output.write_u32::<BigEndian>(header_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&header_data);
output.append(&mut header_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(&key.as_bytes(), &header, &mut output);
}
// IDAT data
let mut idat_data = Vec::with_capacity(self.idat_data.len() + 4);
idat_data.extend_from_slice(b"IDAT");
idat_data.extend(self.idat_data.clone());
output.reserve(idat_data.len() + 8);
output.write_u32::<BigEndian>(idat_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&idat_data);
output.append(&mut idat_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(b"IDAT", &self.idat_data, &mut output);
// Stream end
let iend_data = b"IEND";
output.reserve(iend_data.len() + 8);
output.write_u32::<BigEndian>(0).ok();
let crc = crc32::checksum_ieee(iend_data);
output.extend_from_slice(iend_data);
output.write_u32::<BigEndian>(crc).ok();
write_png_block(b"IEND", &[], &mut output);
output
}
@ -771,7 +718,6 @@ fn reduce_bit_depth_8_or_less(png: &PngData) -> Option<(Vec<u8>, u8)> {
}
for line in png.scan_lines() {
// FIXME: I hate having to iterate twice...
reduced.extend(BitVec::from_bytes(&[line.filter]));
let bit_vec = BitVec::from_bytes(&line.data);
for (i, bit) in bit_vec.iter().enumerate() {
@ -1190,3 +1136,14 @@ fn parse_ihdr_header(byte_data: &[u8]) -> Result<IhdrData, String> {
interlaced: byte_data[12],
})
}
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);
output.write_u32::<BigEndian>(header_data.len() as u32 - 4).ok();
let crc = crc32::checksum_ieee(&header_data);
output.append(&mut header_data);
output.write_u32::<BigEndian>(crc).ok();
}