Refactor filters as enum

benches/filters.rs

@@ -3,7 +3,7 @@
 extern crate oxipng;
 extern crate test;
 
-use oxipng::internal_tests::*;
+use oxipng::{internal_tests::*, RowFilter};
 use std::path::PathBuf;
 use test::Bencher;
 
@@ -13,7 +13,7 @@ fn filters_16_bits_filter_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(0);
+        png.raw.filter_image(RowFilter::None);
     });
 }
 
@@ -23,7 +23,7 @@ fn filters_8_bits_filter_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(0);
+        png.raw.filter_image(RowFilter::None);
     });
 }
 
@@ -35,7 +35,7 @@ fn filters_4_bits_filter_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(0);
+        png.raw.filter_image(RowFilter::None);
     });
 }
 
@@ -47,7 +47,7 @@ fn filters_2_bits_filter_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(0);
+        png.raw.filter_image(RowFilter::None);
     });
 }
 
@@ -59,7 +59,7 @@ fn filters_1_bits_filter_0(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(0);
+        png.raw.filter_image(RowFilter::None);
     });
 }
 
@@ -69,7 +69,7 @@ fn filters_16_bits_filter_1(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(1);
+        png.raw.filter_image(RowFilter::Sub);
     });
 }
 
@@ -79,7 +79,7 @@ fn filters_8_bits_filter_1(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(1);
+        png.raw.filter_image(RowFilter::Sub);
     });
 }
 
@@ -91,7 +91,7 @@ fn filters_4_bits_filter_1(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(1);
+        png.raw.filter_image(RowFilter::Sub);
     });
 }
 
@@ -103,7 +103,7 @@ fn filters_2_bits_filter_1(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(1);
+        png.raw.filter_image(RowFilter::Sub);
     });
 }
 
@@ -115,7 +115,7 @@ fn filters_1_bits_filter_1(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(1);
+        png.raw.filter_image(RowFilter::Sub);
     });
 }
 
@@ -125,7 +125,7 @@ fn filters_16_bits_filter_2(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(2);
+        png.raw.filter_image(RowFilter::Up);
     });
 }
 
@@ -135,7 +135,7 @@ fn filters_8_bits_filter_2(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(2);
+        png.raw.filter_image(RowFilter::Up);
     });
 }
 
@@ -147,7 +147,7 @@ fn filters_4_bits_filter_2(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(2);
+        png.raw.filter_image(RowFilter::Up);
     });
 }
 
@@ -159,7 +159,7 @@ fn filters_2_bits_filter_2(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(2);
+        png.raw.filter_image(RowFilter::Up);
     });
 }
 
@@ -171,7 +171,7 @@ fn filters_1_bits_filter_2(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(2);
+        png.raw.filter_image(RowFilter::Up);
     });
 }
 
@@ -181,7 +181,7 @@ fn filters_16_bits_filter_3(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(3);
+        png.raw.filter_image(RowFilter::Average);
     });
 }
 
@@ -191,7 +191,7 @@ fn filters_8_bits_filter_3(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(3);
+        png.raw.filter_image(RowFilter::Average);
     });
 }
 
@@ -203,7 +203,7 @@ fn filters_4_bits_filter_3(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(3);
+        png.raw.filter_image(RowFilter::Average);
     });
 }
 
@@ -215,7 +215,7 @@ fn filters_2_bits_filter_3(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(3);
+        png.raw.filter_image(RowFilter::Average);
     });
 }
 
@@ -227,7 +227,7 @@ fn filters_1_bits_filter_3(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(3);
+        png.raw.filter_image(RowFilter::Average);
     });
 }
 
@@ -237,7 +237,7 @@ fn filters_16_bits_filter_4(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(4);
+        png.raw.filter_image(RowFilter::Paeth);
     });
 }
 
@@ -247,7 +247,7 @@ fn filters_8_bits_filter_4(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(4);
+        png.raw.filter_image(RowFilter::Paeth);
     });
 }
 
@@ -259,7 +259,7 @@ fn filters_4_bits_filter_4(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(4);
+        png.raw.filter_image(RowFilter::Paeth);
     });
 }
 
@@ -271,7 +271,7 @@ fn filters_2_bits_filter_4(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(4);
+        png.raw.filter_image(RowFilter::Paeth);
     });
 }
 
@@ -283,7 +283,7 @@ fn filters_1_bits_filter_4(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(4);
+        png.raw.filter_image(RowFilter::Paeth);
     });
 }
 
@@ -293,7 +293,7 @@ fn filters_16_bits_filter_5(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(5);
+        png.raw.filter_image(RowFilter::MinSum);
     });
 }
 
@@ -303,7 +303,7 @@ fn filters_8_bits_filter_5(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(5);
+        png.raw.filter_image(RowFilter::MinSum);
     });
 }
 
@@ -315,7 +315,7 @@ fn filters_4_bits_filter_5(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(5);
+        png.raw.filter_image(RowFilter::MinSum);
     });
 }
 
@@ -327,7 +327,7 @@ fn filters_2_bits_filter_5(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(5);
+        png.raw.filter_image(RowFilter::MinSum);
     });
 }
 
@@ -339,6 +339,6 @@ fn filters_1_bits_filter_5(b: &mut Bencher) {
     let png = PngData::new(&input, false).unwrap();
 
     b.iter(|| {
-        png.raw.filter_image(5);
+        png.raw.filter_image(RowFilter::MinSum);
     });
 }

src/evaluate.rs

@@ -3,10 +3,9 @@
 
 use crate::atomicmin::AtomicMin;
 use crate::deflate;
+use crate::filters::RowFilter;
 use crate::png::PngData;
 use crate::png::PngImage;
-use crate::png::STD_COMPRESSION;
-use crate::png::STD_FILTERS;
 #[cfg(not(feature = "parallel"))]
 use crate::rayon;
 use crate::Deadline;
@@ -19,9 +18,13 @@ use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering::SeqCst;
 use std::sync::Arc;
 
+/// Must use normal (lazy) compression, as faster ones (greedy) are not representative
+const STD_COMPRESSION: u8 = 5;
+const STD_FILTERS: [RowFilter; 2] = [RowFilter::None, RowFilter::MinSum];
+
 struct Candidate {
     image: PngData,
-    filter: u8,
+    filter: RowFilter,
     // first wins tie-breaker
     nth: usize,
 }

src/filters.rs

@@ -1,14 +1,61 @@
+use std::{fmt::Display, mem::transmute};
+
 use crate::error::PngError;
 
-pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf: &mut Vec<u8>) {
+#[repr(u8)]
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Hash)]
+pub enum RowFilter {
+    // Standard filter types
+    None,
+    Sub,
+    Up,
+    Average,
+    Paeth,
+    // Heuristic strategies
+    MinSum,
+}
+
+impl TryFrom<u8> for RowFilter {
+    type Error = ();
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        if value > Self::LAST {
+            return Err(());
+        }
+        unsafe { transmute(value as i8) }
+    }
+}
+
+impl Display for RowFilter {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{:8}",
+            match *self {
+                Self::None => "None",
+                Self::Sub => "Sub",
+                Self::Up => "Up",
+                Self::Average => "Average",
+                Self::Paeth => "Paeth",
+                Self::MinSum => "MinSum",
+            }
+        )
+    }
+}
+
+impl RowFilter {
+    pub const LAST: u8 = Self::MinSum as u8;
+    pub const STANDARD: [Self; 5] = [Self::None, Self::Sub, Self::Up, Self::Average, Self::Paeth];
+
+    pub fn filter_line(self, bpp: usize, data: &[u8], last_line: &[u8], buf: &mut Vec<u8>) {
         assert!(data.len() >= bpp);
         assert!(last_line.is_empty() || data.len() == last_line.len());
         buf.reserve(data.len());
-    match filter {
+        match self {
-        0 => {
+            Self::None => {
                 buf.extend_from_slice(data);
             }
-        1 => {
+            Self::Sub => {
                 buf.extend_from_slice(&data[0..bpp]);
                 buf.extend(
                     data.iter()
@@ -17,7 +64,7 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf: &
                         .map(|(cur, last)| cur.wrapping_sub(*last)),
                 );
             }
-        2 => {
+            Self::Up => {
                 if last_line.is_empty() {
                     buf.extend_from_slice(data);
                 } else {
@@ -29,7 +76,7 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf: &
                     );
                 };
             }
-        3 => {
+            Self::Average => {
                 for (i, byte) in data.iter().enumerate() {
                     if last_line.is_empty() {
                         buf.push(match i.checked_sub(bpp) {
@@ -46,7 +93,7 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf: &
                     };
                 }
             }
-        4 => {
+            Self::Paeth => {
                 for (i, byte) in data.iter().enumerate() {
                     if last_line.is_empty() {
                         buf.push(match i.checked_sub(bpp) {
@@ -55,9 +102,11 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf: &
                         });
                     } else {
                         buf.push(match i.checked_sub(bpp) {
-                        Some(x) => {
+                            Some(x) => byte.wrapping_sub(paeth_predictor(
-                            byte.wrapping_sub(paeth_predictor(data[x], last_line[i], last_line[x]))
+                                data[x],
-                        }
+                                last_line[i],
+                                last_line[x],
+                            )),
                             None => byte.wrapping_sub(last_line[i]),
                         });
                     };
@@ -65,24 +114,24 @@ pub fn filter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf: &
             }
             _ => unreachable!(),
         }
-}
+    }
 
-pub fn unfilter_line(
+    pub fn unfilter_line(
-    filter: u8,
+        self,
         bpp: usize,
         data: &[u8],
         last_line: &[u8],
         buf: &mut Vec<u8>,
-) -> Result<(), PngError> {
+    ) -> Result<(), PngError> {
         buf.clear();
         buf.reserve(data.len());
         assert!(data.len() >= bpp);
         assert_eq!(data.len(), last_line.len());
-    match filter {
+        match self {
-        0 => {
+            Self::None => {
                 buf.extend_from_slice(data);
             }
-        1 => {
+            Self::Sub => {
                 for (i, &cur) in data.iter().enumerate() {
                     let prev_byte = i.checked_sub(bpp).and_then(|x| buf.get(x).copied());
                     buf.push(match prev_byte {
@@ -91,14 +140,14 @@ pub fn unfilter_line(
                     });
                 }
             }
-        2 => {
+            Self::Up => {
                 buf.extend(
                     data.iter()
                         .zip(last_line)
                         .map(|(&cur, &last)| cur.wrapping_add(last)),
                 );
             }
-        3 => {
+            Self::Average => {
                 for (i, (&cur, &last)) in data.iter().zip(last_line).enumerate() {
                     let prev_byte = i.checked_sub(bpp).and_then(|x| buf.get(x).copied());
                     buf.push(match prev_byte {
@@ -107,7 +156,7 @@ pub fn unfilter_line(
                     });
                 }
             }
-        4 => {
+            Self::Paeth => {
                 for (i, (&cur, &up)) in data.iter().zip(last_line).enumerate() {
                     buf.push(
                         match i
@@ -125,6 +174,7 @@ pub fn unfilter_line(
             _ => return Err(PngError::InvalidData),
         }
         Ok(())
+    }
 }
 
 fn paeth_predictor(a: u8, b: u8, c: u8) -> u8 {

src/lib.rs

@@ -45,6 +45,7 @@ use std::time::{Duration, Instant};
 pub use crate::colors::AlphaOptim;
 pub use crate::deflate::Deflaters;
 pub use crate::error::PngError;
+pub use crate::filters::RowFilter;
 pub use crate::headers::Headers;
 pub use indexmap::{IndexMap, IndexSet};
 
@@ -149,7 +150,7 @@ pub struct Options {
     /// Which filters to try on the file (0-5)
     ///
     /// Default: `0,5`
-    pub filter: IndexSet<u8>,
+    pub filter: IndexSet<RowFilter>,
     /// Whether to change the interlacing type of the file.
     ///
     /// `None` will not change the current interlacing type.
@@ -253,9 +254,10 @@ impl Options {
     }
 
     fn apply_preset_3(mut self) -> Self {
-        for i in 1..=4 {
+        self.filter.insert(RowFilter::Sub);
-            self.filter.insert(i);
+        self.filter.insert(RowFilter::Up);
-        }
+        self.filter.insert(RowFilter::Average);
+        self.filter.insert(RowFilter::Paeth);
         self
     }
 
@@ -292,8 +294,8 @@ impl Default for Options {
     fn default() -> Options {
         // Default settings based on -o 2 from the CLI interface
         let mut filter = IndexSet::new();
-        filter.insert(0);
+        filter.insert(RowFilter::None);
-        filter.insert(5);
+        filter.insert(RowFilter::MinSum);
         let mut compression = IndexSet::new();
         compression.insert(11);
         // We always need NoOp to be present
@@ -465,7 +467,7 @@ pub fn optimize_from_memory(data: &[u8], opts: &Options) -> PngResult<Vec<u8>> {
 #[derive(Debug, PartialEq, PartialOrd, Clone, Copy)]
 /// Defines options to be used for a single compression trial
 struct TrialOptions {
-    pub filter: u8,
+    pub filter: RowFilter,
     pub compression: u8,
 }
 
@@ -511,9 +513,9 @@ fn optimize_png(
         let use_filter = if png.raw.ihdr.bit_depth.as_u8() >= 8
             && png.raw.ihdr.color_type != colors::ColorType::Indexed
         {
-            5
+            RowFilter::MinSum
         } else {
-            0
+            RowFilter::None
         };
         if filter.is_empty() {
             filter.insert(use_filter);
@@ -570,7 +572,7 @@ fn optimize_png(
 
         info!("Trying: {} combinations", results.len());
 
-        let filters: IndexMap<u8, Vec<u8>> = filter
+        let filters: IndexMap<RowFilter, Vec<u8>> = filter
             .par_iter()
             .with_max_len(1)
             .map(|f| {

src/main.rs

@@ -20,6 +20,7 @@ use oxipng::AlphaOptim;
 use oxipng::Deflaters;
 use oxipng::Headers;
 use oxipng::Options;
+use oxipng::RowFilter;
 use oxipng::{InFile, OutFile};
 use std::fs::DirBuilder;
 #[cfg(feature = "zopfli")]
@@ -168,11 +169,15 @@ fn main() {
         )
         .arg(
             Arg::new("filters")
-                .help("PNG delta filters (0-5) - Default: 0,5")
+                .help(&*format!(
+                    "PNG delta filters (0-{}) - Default: 0,{}",
+                    RowFilter::LAST,
+                    RowFilter::MinSum as u8
+                ))
                 .short('f')
                 .long("filters")
                 .takes_value(true)
-                .validator(|x| match parse_numeric_range_opts(x, 0, 5) {
+                .validator(|x| match parse_numeric_range_opts(x, 0, RowFilter::LAST) {
                     Ok(_) => Ok(()),
                     Err(_) => Err("Invalid option for filters".to_owned()),
                 }),
@@ -381,7 +386,10 @@ fn parse_opts_into_struct(
     }
 
     if let Some(x) = matches.value_of("filters") {
-        opts.filter = parse_numeric_range_opts(x, 0, 5).unwrap();
+        opts.filter.clear();
+        for f in parse_numeric_range_opts(x, 0, RowFilter::LAST).unwrap() {
+            opts.filter.insert(RowFilter::try_from(f).unwrap());
+        }
     }
 
     if let Some(x) = matches.value_of("timeout") {

src/png/mod.rs

@@ -13,10 +13,6 @@ use std::iter::Iterator;
 use std::path::Path;
 use std::sync::Arc;
 
-/// Must use normal (lazy) compression, as faster ones (greedy) are not representative
-pub(crate) const STD_COMPRESSION: u8 = 5;
-pub(crate) const STD_FILTERS: [u8; 2] = [0, 5];
-
 pub(crate) mod scan_lines;
 
 use self::scan_lines::{ScanLines, ScanLinesMut};
@@ -292,7 +288,8 @@ impl PngImage {
                 last_pass = line.pass;
             }
             last_line.resize(line.data.len(), 0);
-            unfilter_line(line.filter, bpp, line.data, &last_line, &mut unfiltered_buf)?;
+            let filter = RowFilter::try_from(line.filter).map_err(|_| PngError::InvalidData)?;
+            filter.unfilter_line(bpp, line.data, &last_line, &mut unfiltered_buf)?;
             unfiltered.push(0);
             unfiltered.extend_from_slice(&unfiltered_buf);
             std::mem::swap(&mut last_line, &mut unfiltered_buf);
@@ -302,13 +299,7 @@ impl PngImage {
     }
 
     /// Apply the specified filter type to all rows in the image
-    /// 0: None
+    pub fn filter_image(&self, filter: RowFilter) -> Vec<u8> {
-    /// 1: Sub
-    /// 2: Up
-    /// 3: Average
-    /// 4: Paeth
-    /// 5: All (heuristically pick the best filter for each line)
-    pub fn filter_image(&self, filter: u8) -> Vec<u8> {
         let mut filtered = Vec::with_capacity(self.data.len());
         let bpp = ((self.ihdr.bit_depth.as_u8() * self.channels_per_pixel() + 7) / 8) as usize;
         let mut last_line: &[u8] = &[];
@@ -320,42 +311,44 @@ impl PngImage {
                 last_line = &[];
             }
             match filter {
-                0 | 1 | 2 | 3 | 4 => {
+                RowFilter::MinSum => {
-                    let filter = if last_pass == line.pass || filter <= 1 {
-                        filter
-                    } else {
-                        0
-                    };
-                    filtered.push(filter);
-                    filter_line(filter, bpp, line.data, last_line, &mut f_buf);
-                    filtered.extend_from_slice(&f_buf);
-                }
-                5 => {
                     // Heuristically guess best filter per line
                     // Uses MSAD algorithm mentioned in libpng reference docs
                     // http://www.libpng.org/pub/png/book/chapter09.html
-                    let mut best_filter = 0;
+                    let mut best_filter = RowFilter::None;
                     let mut best_line = Vec::new();
                     let mut best_size = u64::MAX;
 
+                    for try_filter in RowFilter::STANDARD {
                         // Avoid vertical filtering on first line of each interlacing pass
-                    for filter in if last_pass == line.pass { 0..5 } else { 0..2 } {
+                        if last_pass != line.pass && try_filter > RowFilter::Sub {
-                        filter_line(filter, bpp, line.data, last_line, &mut f_buf);
+                            continue;
+                        }
+                        try_filter.filter_line(bpp, line.data, last_line, &mut f_buf);
                         let size = f_buf.iter().fold(0_u64, |acc, &x| {
                             let signed = x as i8;
                             acc + i16::from(signed).unsigned_abs() as u64
                         });
                         if size < best_size {
                             best_size = size;
-                            best_filter = filter;
+                            best_filter = try_filter;
                             std::mem::swap(&mut best_line, &mut f_buf);
                         }
                         f_buf.clear() //discard buffer, and start again
                     }
-                    filtered.push(best_filter);
+                    filtered.push(best_filter as u8);
                     filtered.extend_from_slice(&best_line);
                 }
-                _ => unreachable!(),
+                _ => {
+                    let filter = if last_pass == line.pass || filter <= RowFilter::Sub {
+                        filter
+                    } else {
+                        RowFilter::None
+                    };
+                    filtered.push(filter as u8);
+                    filter.filter_line(bpp, line.data, last_line, &mut f_buf);
+                    filtered.extend_from_slice(&f_buf);
+                }
             }
             last_line = line.data;
             last_pass = line.pass;

tests/filters.rs

@@ -1,5 +1,5 @@
 use indexmap::IndexSet;
-use oxipng::internal_tests::*;
+use oxipng::{internal_tests::*, RowFilter};
 use oxipng::{InFile, OutFile};
 use std::fs::remove_file;
 use std::path::Path;
@@ -11,7 +11,7 @@ fn get_opts(input: &Path) -> (OutFile, oxipng::Options) {
         ..Default::default()
     };
     let mut filter = IndexSet::new();
-    filter.insert(0);
+    filter.insert(RowFilter::None);
     options.filter = filter;
 
     (
@@ -22,7 +22,7 @@ fn get_opts(input: &Path) -> (OutFile, oxipng::Options) {
 
 fn test_it_converts(
     input: &str,
-    filter: u8,
+    filter: RowFilter,
     color_type_in: ColorType,
     bit_depth_in: BitDepth,
     color_type_out: ColorType,
@@ -67,7 +67,7 @@ fn test_it_converts(
 fn filter_0_for_rgba_16() {
     test_it_converts(
         "tests/files/filter_0_for_rgba_16.png",
-        0,
+        RowFilter::None,
         ColorType::RGBA,
         BitDepth::Sixteen,
         ColorType::RGBA,
@@ -79,7 +79,7 @@ fn filter_0_for_rgba_16() {
 fn filter_1_for_rgba_16() {
     test_it_converts(
         "tests/files/filter_1_for_rgba_16.png",
-        1,
+        RowFilter::Sub,
         ColorType::RGBA,
         BitDepth::Sixteen,
         ColorType::RGBA,
@@ -91,7 +91,7 @@ fn filter_1_for_rgba_16() {
 fn filter_2_for_rgba_16() {
     test_it_converts(
         "tests/files/filter_2_for_rgba_16.png",
-        2,
+        RowFilter::Up,
         ColorType::RGBA,
         BitDepth::Sixteen,
         ColorType::RGBA,
@@ -103,7 +103,7 @@ fn filter_2_for_rgba_16() {
 fn filter_3_for_rgba_16() {
     test_it_converts(
         "tests/files/filter_3_for_rgba_16.png",
-        3,
+        RowFilter::Average,
         ColorType::RGBA,
         BitDepth::Sixteen,
         ColorType::RGBA,
@@ -115,7 +115,7 @@ fn filter_3_for_rgba_16() {
 fn filter_4_for_rgba_16() {
     test_it_converts(
         "tests/files/filter_4_for_rgba_16.png",
-        4,
+        RowFilter::Paeth,
         ColorType::RGBA,
         BitDepth::Sixteen,
         ColorType::RGBA,
@@ -127,7 +127,7 @@ fn filter_4_for_rgba_16() {
 fn filter_5_for_rgba_16() {
     test_it_converts(
         "tests/files/filter_5_for_rgba_16.png",
-        5,
+        RowFilter::MinSum,
         ColorType::RGBA,
         BitDepth::Sixteen,
         ColorType::RGBA,
@@ -139,7 +139,7 @@ fn filter_5_for_rgba_16() {
 fn filter_0_for_rgba_8() {
     test_it_converts(
         "tests/files/filter_0_for_rgba_8.png",
-        0,
+        RowFilter::None,
         ColorType::RGBA,
         BitDepth::Eight,
         ColorType::RGBA,
@@ -151,7 +151,7 @@ fn filter_0_for_rgba_8() {
 fn filter_1_for_rgba_8() {
     test_it_converts(
         "tests/files/filter_1_for_rgba_8.png",
-        1,
+        RowFilter::Sub,
         ColorType::RGBA,
         BitDepth::Eight,
         ColorType::RGBA,
@@ -163,7 +163,7 @@ fn filter_1_for_rgba_8() {
 fn filter_2_for_rgba_8() {
     test_it_converts(
         "tests/files/filter_2_for_rgba_8.png",
-        2,
+        RowFilter::Up,
         ColorType::RGBA,
         BitDepth::Eight,
         ColorType::RGBA,
@@ -175,7 +175,7 @@ fn filter_2_for_rgba_8() {
 fn filter_3_for_rgba_8() {
     test_it_converts(
         "tests/files/filter_3_for_rgba_8.png",
-        3,
+        RowFilter::Average,
         ColorType::RGBA,
         BitDepth::Eight,
         ColorType::RGBA,
@@ -187,7 +187,7 @@ fn filter_3_for_rgba_8() {
 fn filter_4_for_rgba_8() {
     test_it_converts(
         "tests/files/filter_4_for_rgba_8.png",
-        4,
+        RowFilter::Paeth,
         ColorType::RGBA,
         BitDepth::Eight,
         ColorType::RGBA,
@@ -199,7 +199,7 @@ fn filter_4_for_rgba_8() {
 fn filter_5_for_rgba_8() {
     test_it_converts(
         "tests/files/filter_5_for_rgba_8.png",
-        5,
+        RowFilter::MinSum,
         ColorType::RGBA,
         BitDepth::Eight,
         ColorType::RGBA,
@@ -211,7 +211,7 @@ fn filter_5_for_rgba_8() {
 fn filter_0_for_rgb_16() {
     test_it_converts(
         "tests/files/filter_0_for_rgb_16.png",
-        0,
+        RowFilter::None,
         ColorType::RGB,
         BitDepth::Sixteen,
         ColorType::RGB,
@@ -223,7 +223,7 @@ fn filter_0_for_rgb_16() {
 fn filter_1_for_rgb_16() {
     test_it_converts(
         "tests/files/filter_1_for_rgb_16.png",
-        1,
+        RowFilter::Sub,
         ColorType::RGB,
         BitDepth::Sixteen,
         ColorType::RGB,
@@ -235,7 +235,7 @@ fn filter_1_for_rgb_16() {
 fn filter_2_for_rgb_16() {
     test_it_converts(
         "tests/files/filter_2_for_rgb_16.png",
-        2,
+        RowFilter::Up,
         ColorType::RGB,
         BitDepth::Sixteen,
         ColorType::RGB,
@@ -247,7 +247,7 @@ fn filter_2_for_rgb_16() {
 fn filter_3_for_rgb_16() {
     test_it_converts(
         "tests/files/filter_3_for_rgb_16.png",
-        3,
+        RowFilter::Average,
         ColorType::RGB,
         BitDepth::Sixteen,
         ColorType::RGB,
@@ -259,7 +259,7 @@ fn filter_3_for_rgb_16() {
 fn filter_4_for_rgb_16() {
     test_it_converts(
         "tests/files/filter_4_for_rgb_16.png",
-        4,
+        RowFilter::Paeth,
         ColorType::RGB,
         BitDepth::Sixteen,
         ColorType::RGB,
@@ -271,7 +271,7 @@ fn filter_4_for_rgb_16() {
 fn filter_5_for_rgb_16() {
     test_it_converts(
         "tests/files/filter_5_for_rgb_16.png",
-        5,
+        RowFilter::MinSum,
         ColorType::RGB,
         BitDepth::Sixteen,
         ColorType::RGB,
@@ -283,7 +283,7 @@ fn filter_5_for_rgb_16() {
 fn filter_0_for_rgb_8() {
     test_it_converts(
         "tests/files/filter_0_for_rgb_8.png",
-        0,
+        RowFilter::None,
         ColorType::RGB,
         BitDepth::Eight,
         ColorType::RGB,
@@ -295,7 +295,7 @@ fn filter_0_for_rgb_8() {
 fn filter_1_for_rgb_8() {
     test_it_converts(
         "tests/files/filter_1_for_rgb_8.png",
-        1,
+        RowFilter::Sub,
         ColorType::RGB,
         BitDepth::Eight,
         ColorType::RGB,
@@ -307,7 +307,7 @@ fn filter_1_for_rgb_8() {
 fn filter_2_for_rgb_8() {
     test_it_converts(
         "tests/files/filter_2_for_rgb_8.png",
-        2,
+        RowFilter::Up,
         ColorType::RGB,
         BitDepth::Eight,
         ColorType::RGB,
@@ -319,7 +319,7 @@ fn filter_2_for_rgb_8() {
 fn filter_3_for_rgb_8() {
     test_it_converts(
         "tests/files/filter_3_for_rgb_8.png",
-        3,
+        RowFilter::Average,
         ColorType::RGB,
         BitDepth::Eight,
         ColorType::RGB,
@@ -331,7 +331,7 @@ fn filter_3_for_rgb_8() {
 fn filter_4_for_rgb_8() {
     test_it_converts(
         "tests/files/filter_4_for_rgb_8.png",
-        4,
+        RowFilter::Paeth,
         ColorType::RGB,
         BitDepth::Eight,
         ColorType::RGB,
@@ -343,7 +343,7 @@ fn filter_4_for_rgb_8() {
 fn filter_5_for_rgb_8() {
     test_it_converts(
         "tests/files/filter_5_for_rgb_8.png",
-        5,
+        RowFilter::MinSum,
         ColorType::RGB,
         BitDepth::Eight,
         ColorType::RGB,
@@ -355,7 +355,7 @@ fn filter_5_for_rgb_8() {
 fn filter_0_for_grayscale_alpha_16() {
     test_it_converts(
         "tests/files/filter_0_for_grayscale_alpha_16.png",
-        0,
+        RowFilter::None,
         ColorType::GrayscaleAlpha,
         BitDepth::Sixteen,
         ColorType::GrayscaleAlpha,
@@ -367,7 +367,7 @@ fn filter_0_for_grayscale_alpha_16() {
 fn filter_1_for_grayscale_alpha_16() {
     test_it_converts(
         "tests/files/filter_1_for_grayscale_alpha_16.png",
-        1,
+        RowFilter::Sub,
         ColorType::GrayscaleAlpha,
         BitDepth::Sixteen,
         ColorType::GrayscaleAlpha,
@@ -379,7 +379,7 @@ fn filter_1_for_grayscale_alpha_16() {
 fn filter_2_for_grayscale_alpha_16() {
     test_it_converts(
         "tests/files/filter_2_for_grayscale_alpha_16.png",
-        2,
+        RowFilter::Up,
         ColorType::GrayscaleAlpha,
         BitDepth::Sixteen,
         ColorType::GrayscaleAlpha,
@@ -391,7 +391,7 @@ fn filter_2_for_grayscale_alpha_16() {
 fn filter_3_for_grayscale_alpha_16() {
     test_it_converts(
         "tests/files/filter_3_for_grayscale_alpha_16.png",
-        3,
+        RowFilter::Average,
         ColorType::GrayscaleAlpha,
         BitDepth::Sixteen,
         ColorType::GrayscaleAlpha,
@@ -403,7 +403,7 @@ fn filter_3_for_grayscale_alpha_16() {
 fn filter_4_for_grayscale_alpha_16() {
     test_it_converts(
         "tests/files/filter_4_for_grayscale_alpha_16.png",
-        4,
+        RowFilter::Paeth,
         ColorType::GrayscaleAlpha,
         BitDepth::Sixteen,
         ColorType::GrayscaleAlpha,
@@ -415,7 +415,7 @@ fn filter_4_for_grayscale_alpha_16() {
 fn filter_5_for_grayscale_alpha_16() {
     test_it_converts(
         "tests/files/filter_5_for_grayscale_alpha_16.png",
-        5,
+        RowFilter::MinSum,
         ColorType::GrayscaleAlpha,
         BitDepth::Sixteen,
         ColorType::GrayscaleAlpha,
@@ -427,7 +427,7 @@ fn filter_5_for_grayscale_alpha_16() {
 fn filter_0_for_grayscale_alpha_8() {
     test_it_converts(
         "tests/files/filter_0_for_grayscale_alpha_8.png",
-        0,
+        RowFilter::None,
         ColorType::GrayscaleAlpha,
         BitDepth::Eight,
         ColorType::GrayscaleAlpha,
@@ -439,7 +439,7 @@ fn filter_0_for_grayscale_alpha_8() {
 fn filter_1_for_grayscale_alpha_8() {
     test_it_converts(
         "tests/files/filter_1_for_grayscale_alpha_8.png",
-        1,
+        RowFilter::Sub,
         ColorType::GrayscaleAlpha,
         BitDepth::Eight,
         ColorType::GrayscaleAlpha,
@@ -451,7 +451,7 @@ fn filter_1_for_grayscale_alpha_8() {
 fn filter_2_for_grayscale_alpha_8() {
     test_it_converts(
         "tests/files/filter_2_for_grayscale_alpha_8.png",
-        2,
+        RowFilter::Up,
         ColorType::GrayscaleAlpha,
         BitDepth::Eight,
         ColorType::GrayscaleAlpha,
@@ -463,7 +463,7 @@ fn filter_2_for_grayscale_alpha_8() {
 fn filter_3_for_grayscale_alpha_8() {
     test_it_converts(
         "tests/files/filter_3_for_grayscale_alpha_8.png",
-        3,
+        RowFilter::Average,
         ColorType::GrayscaleAlpha,
         BitDepth::Eight,
         ColorType::GrayscaleAlpha,
@@ -475,7 +475,7 @@ fn filter_3_for_grayscale_alpha_8() {
 fn filter_4_for_grayscale_alpha_8() {
     test_it_converts(
         "tests/files/filter_4_for_grayscale_alpha_8.png",
-        4,
+        RowFilter::Paeth,
         ColorType::GrayscaleAlpha,
         BitDepth::Eight,
         ColorType::GrayscaleAlpha,
@@ -487,7 +487,7 @@ fn filter_4_for_grayscale_alpha_8() {
 fn filter_5_for_grayscale_alpha_8() {
     test_it_converts(
         "tests/files/filter_5_for_grayscale_alpha_8.png",
-        5,
+        RowFilter::MinSum,
         ColorType::GrayscaleAlpha,
         BitDepth::Eight,
         ColorType::GrayscaleAlpha,
@@ -499,7 +499,7 @@ fn filter_5_for_grayscale_alpha_8() {
 fn filter_0_for_grayscale_16() {
     test_it_converts(
         "tests/files/filter_0_for_grayscale_16.png",
-        0,
+        RowFilter::None,
         ColorType::Grayscale,
         BitDepth::Sixteen,
         ColorType::Grayscale,
@@ -511,7 +511,7 @@ fn filter_0_for_grayscale_16() {
 fn filter_1_for_grayscale_16() {
     test_it_converts(
         "tests/files/filter_1_for_grayscale_16.png",
-        1,
+        RowFilter::Sub,
         ColorType::Grayscale,
         BitDepth::Sixteen,
         ColorType::Grayscale,
@@ -523,7 +523,7 @@ fn filter_1_for_grayscale_16() {
 fn filter_2_for_grayscale_16() {
     test_it_converts(
         "tests/files/filter_2_for_grayscale_16.png",
-        2,
+        RowFilter::Up,
         ColorType::Grayscale,
         BitDepth::Sixteen,
         ColorType::Grayscale,
@@ -535,7 +535,7 @@ fn filter_2_for_grayscale_16() {
 fn filter_3_for_grayscale_16() {
     test_it_converts(
         "tests/files/filter_3_for_grayscale_16.png",
-        3,
+        RowFilter::Average,
         ColorType::Grayscale,
         BitDepth::Sixteen,
         ColorType::Grayscale,
@@ -547,7 +547,7 @@ fn filter_3_for_grayscale_16() {
 fn filter_4_for_grayscale_16() {
     test_it_converts(
         "tests/files/filter_4_for_grayscale_16.png",
-        4,
+        RowFilter::Paeth,
         ColorType::Grayscale,
         BitDepth::Sixteen,
         ColorType::Grayscale,
@@ -559,7 +559,7 @@ fn filter_4_for_grayscale_16() {
 fn filter_5_for_grayscale_16() {
     test_it_converts(
         "tests/files/filter_5_for_grayscale_16.png",
-        5,
+        RowFilter::MinSum,
         ColorType::Grayscale,
         BitDepth::Sixteen,
         ColorType::Grayscale,
@@ -571,7 +571,7 @@ fn filter_5_for_grayscale_16() {
 fn filter_0_for_grayscale_8() {
     test_it_converts(
         "tests/files/filter_0_for_grayscale_8.png",
-        0,
+        RowFilter::None,
         ColorType::Grayscale,
         BitDepth::Eight,
         ColorType::Grayscale,
@@ -583,7 +583,7 @@ fn filter_0_for_grayscale_8() {
 fn filter_1_for_grayscale_8() {
     test_it_converts(
         "tests/files/filter_1_for_grayscale_8.png",
-        1,
+        RowFilter::Sub,
         ColorType::Grayscale,
         BitDepth::Eight,
         ColorType::Grayscale,
@@ -595,7 +595,7 @@ fn filter_1_for_grayscale_8() {
 fn filter_2_for_grayscale_8() {
     test_it_converts(
         "tests/files/filter_2_for_grayscale_8.png",
-        2,
+        RowFilter::Up,
         ColorType::Grayscale,
         BitDepth::Eight,
         ColorType::Grayscale,
@@ -607,7 +607,7 @@ fn filter_2_for_grayscale_8() {
 fn filter_3_for_grayscale_8() {
     test_it_converts(
         "tests/files/filter_3_for_grayscale_8.png",
-        3,
+        RowFilter::Average,
         ColorType::Grayscale,
         BitDepth::Eight,
         ColorType::Grayscale,
@@ -619,7 +619,7 @@ fn filter_3_for_grayscale_8() {
 fn filter_4_for_grayscale_8() {
     test_it_converts(
         "tests/files/filter_4_for_grayscale_8.png",
-        4,
+        RowFilter::Paeth,
         ColorType::Grayscale,
         BitDepth::Eight,
         ColorType::Grayscale,
@@ -631,7 +631,7 @@ fn filter_4_for_grayscale_8() {
 fn filter_5_for_grayscale_8() {
     test_it_converts(
         "tests/files/filter_5_for_grayscale_8.png",
-        5,
+        RowFilter::MinSum,
         ColorType::Grayscale,
         BitDepth::Eight,
         ColorType::Grayscale,
@@ -643,7 +643,7 @@ fn filter_5_for_grayscale_8() {
 fn filter_0_for_palette_4() {
     test_it_converts(
         "tests/files/filter_0_for_palette_4.png",
-        0,
+        RowFilter::None,
         ColorType::Indexed,
         BitDepth::Four,
         ColorType::Indexed,
@@ -655,7 +655,7 @@ fn filter_0_for_palette_4() {
 fn filter_1_for_palette_4() {
     test_it_converts(
         "tests/files/filter_1_for_palette_4.png",
-        1,
+        RowFilter::Sub,
         ColorType::Indexed,
         BitDepth::Four,
         ColorType::Indexed,
@@ -667,7 +667,7 @@ fn filter_1_for_palette_4() {
 fn filter_2_for_palette_4() {
     test_it_converts(
         "tests/files/filter_2_for_palette_4.png",
-        2,
+        RowFilter::Up,
         ColorType::Indexed,
         BitDepth::Four,
         ColorType::Indexed,
@@ -679,7 +679,7 @@ fn filter_2_for_palette_4() {
 fn filter_3_for_palette_4() {
     test_it_converts(
         "tests/files/filter_3_for_palette_4.png",
-        3,
+        RowFilter::Average,
         ColorType::Indexed,
         BitDepth::Four,
         ColorType::Indexed,
@@ -691,7 +691,7 @@ fn filter_3_for_palette_4() {
 fn filter_4_for_palette_4() {
     test_it_converts(
         "tests/files/filter_4_for_palette_4.png",
-        4,
+        RowFilter::Paeth,
         ColorType::Indexed,
         BitDepth::Four,
         ColorType::Indexed,
@@ -703,7 +703,7 @@ fn filter_4_for_palette_4() {
 fn filter_5_for_palette_4() {
     test_it_converts(
         "tests/files/filter_5_for_palette_4.png",
-        5,
+        RowFilter::MinSum,
         ColorType::Indexed,
         BitDepth::Four,
         ColorType::Indexed,
@@ -715,7 +715,7 @@ fn filter_5_for_palette_4() {
 fn filter_0_for_palette_2() {
     test_it_converts(
         "tests/files/filter_0_for_palette_2.png",
-        0,
+        RowFilter::None,
         ColorType::Indexed,
         BitDepth::Two,
         ColorType::Indexed,
@@ -727,7 +727,7 @@ fn filter_0_for_palette_2() {
 fn filter_1_for_palette_2() {
     test_it_converts(
         "tests/files/filter_1_for_palette_2.png",
-        1,
+        RowFilter::Sub,
         ColorType::Indexed,
         BitDepth::Two,
         ColorType::Indexed,
@@ -739,7 +739,7 @@ fn filter_1_for_palette_2() {
 fn filter_2_for_palette_2() {
     test_it_converts(
         "tests/files/filter_2_for_palette_2.png",
-        2,
+        RowFilter::Up,
         ColorType::Indexed,
         BitDepth::Two,
         ColorType::Indexed,
@@ -751,7 +751,7 @@ fn filter_2_for_palette_2() {
 fn filter_3_for_palette_2() {
     test_it_converts(
         "tests/files/filter_3_for_palette_2.png",
-        3,
+        RowFilter::Average,
         ColorType::Indexed,
         BitDepth::Two,
         ColorType::Indexed,
@@ -763,7 +763,7 @@ fn filter_3_for_palette_2() {
 fn filter_4_for_palette_2() {
     test_it_converts(
         "tests/files/filter_4_for_palette_2.png",
-        4,
+        RowFilter::Paeth,
         ColorType::Indexed,
         BitDepth::Two,
         ColorType::Indexed,
@@ -775,7 +775,7 @@ fn filter_4_for_palette_2() {
 fn filter_5_for_palette_2() {
     test_it_converts(
         "tests/files/filter_5_for_palette_2.png",
-        5,
+        RowFilter::MinSum,
         ColorType::Indexed,
         BitDepth::Two,
         ColorType::Indexed,
@@ -787,7 +787,7 @@ fn filter_5_for_palette_2() {
 fn filter_0_for_palette_1() {
     test_it_converts(
         "tests/files/filter_0_for_palette_1.png",
-        0,
+        RowFilter::None,
         ColorType::Indexed,
         BitDepth::One,
         ColorType::Indexed,
@@ -799,7 +799,7 @@ fn filter_0_for_palette_1() {
 fn filter_1_for_palette_1() {
     test_it_converts(
         "tests/files/filter_1_for_palette_1.png",
-        1,
+        RowFilter::Sub,
         ColorType::Indexed,
         BitDepth::One,
         ColorType::Indexed,
@@ -811,7 +811,7 @@ fn filter_1_for_palette_1() {
 fn filter_2_for_palette_1() {
     test_it_converts(
         "tests/files/filter_2_for_palette_1.png",
-        2,
+        RowFilter::Up,
         ColorType::Indexed,
         BitDepth::One,
         ColorType::Indexed,
@@ -823,7 +823,7 @@ fn filter_2_for_palette_1() {
 fn filter_3_for_palette_1() {
     test_it_converts(
         "tests/files/filter_3_for_palette_1.png",
-        3,
+        RowFilter::Average,
         ColorType::Indexed,
         BitDepth::One,
         ColorType::Indexed,
@@ -835,7 +835,7 @@ fn filter_3_for_palette_1() {
 fn filter_4_for_palette_1() {
     test_it_converts(
         "tests/files/filter_4_for_palette_1.png",
-        4,
+        RowFilter::Paeth,
         ColorType::Indexed,
         BitDepth::One,
         ColorType::Indexed,
@@ -847,7 +847,7 @@ fn filter_4_for_palette_1() {
 fn filter_5_for_palette_1() {
     test_it_converts(
         "tests/files/filter_5_for_palette_1.png",
-        5,
+        RowFilter::MinSum,
         ColorType::Indexed,
         BitDepth::One,
         ColorType::Indexed,

tests/flags.rs

@@ -1,5 +1,5 @@
 use indexmap::IndexSet;
-use oxipng::internal_tests::*;
+use oxipng::{internal_tests::*, RowFilter};
 use oxipng::{InFile, OutFile};
 #[cfg(feature = "filetime")]
 use std::cell::RefCell;
@@ -16,7 +16,7 @@ fn get_opts(input: &Path) -> (OutFile, oxipng::Options) {
         ..Default::default()
     };
     let mut filter = IndexSet::new();
-    filter.insert(0);
+    filter.insert(RowFilter::None);
     options.filter = filter;
 
     (
@@ -173,7 +173,7 @@ fn verbose_mode() {
     assert_eq!(logs.len(), 1);
     logs.sort();
     for (i, log) in logs.into_iter().enumerate() {
-        let expected_prefix = format!("    zc = 11  f = 0 ");
+        let expected_prefix = format!("    zc = 11  f = None ");
         assert!(
             log.starts_with(&expected_prefix),
             "logs[{}] = {:?} doesn't start with {:?}",
@@ -454,7 +454,7 @@ fn interlaced_0_to_1_other_filter_mode() {
     let (output, mut opts) = get_opts(&input);
     opts.interlace = Some(1);
     let mut filter = IndexSet::new();
-    filter.insert(4);
+    filter.insert(RowFilter::Paeth);
     opts.filter = filter;
 
     let png = PngData::new(&input, opts.fix_errors).unwrap();

tests/interlaced.rs

@@ -1,5 +1,5 @@
 use indexmap::IndexSet;
-use oxipng::internal_tests::*;
+use oxipng::{internal_tests::*, RowFilter};
 use oxipng::{InFile, OutFile};
 use std::fs::remove_file;
 use std::path::Path;
@@ -11,7 +11,7 @@ fn get_opts(input: &Path) -> (OutFile, oxipng::Options) {
         ..Default::default()
     };
     let mut filter = IndexSet::new();
-    filter.insert(0);
+    filter.insert(RowFilter::None);
     options.filter = filter;
 
     (

tests/reduction.rs

@@ -1,5 +1,5 @@
 use indexmap::IndexSet;
-use oxipng::internal_tests::*;
+use oxipng::{internal_tests::*, RowFilter};
 use oxipng::{InFile, OutFile};
 use std::fs::remove_file;
 use std::path::Path;
@@ -11,7 +11,7 @@ fn get_opts(input: &Path) -> (OutFile, oxipng::Options) {
         ..Default::default()
     };
     let mut filter = IndexSet::new();
-    filter.insert(0);
+    filter.insert(RowFilter::None);
     options.filter = filter;
 
     (

tests/regression.rs

@@ -1,5 +1,5 @@
 use indexmap::IndexSet;
-use oxipng::internal_tests::*;
+use oxipng::{internal_tests::*, RowFilter};
 use oxipng::{InFile, OutFile};
 use std::fs::remove_file;
 use std::path::Path;
@@ -11,7 +11,7 @@ fn get_opts(input: &Path) -> (OutFile, oxipng::Options) {
         ..Default::default()
     };
     let mut filter = IndexSet::new();
-    filter.insert(0);
+    filter.insert(RowFilter::None);
     options.filter = filter;
 
     (
@@ -288,7 +288,7 @@ fn issue_92_filter_0() {
 fn issue_92_filter_5() {
     let input = "tests/files/issue-92.png";
     let (_, mut opts) = get_opts(Path::new(input));
-    opts.filter = [5].iter().cloned().collect();
+    opts.filter = [RowFilter::MinSum].iter().cloned().collect();
     let output = OutFile::Path(Some(Path::new(input).with_extension("-f5-out.png")));
 
     test_it_converts(