Skip extra evaluation when identical

src/reduction/mod.rs

@@ -143,22 +143,23 @@ pub(crate) fn perform_reductions(
 
  // Attempt to reduce to a lower bit depth
  if opts.bit_depth_reduction && !deadline.passed() {
- // First try reducing the `png` var (could be grayscale or indexed)
+ // First try the `png` var
  let reduced = reduced_bit_depth_8_or_less(&png);
- // It's possible that an indexed version will be smaller (it might reach a lower depth),
- // but grayscale is usually better so we'll skip it if we're doing cheap evaluations and
- // already have a reduced image.
- let try_indexed = !cheap || reduced.is_none();
+ // Then try the `indexed` var, unless we're doing cheap evaluations and already have a reduction
+ if (!cheap || reduced.is_none()) && !deadline.passed() {
+ if let Some(indexed) = indexed.and_then(|png| reduced_bit_depth_8_or_less(&png)) {
+ // Only evaluate this if it's different from the first result (which must be grayscale if it exists)
+ if reduced.as_ref().map_or(true, |r| r.data != indexed.data) {
+ eval.try_image(Arc::new(indexed));
+ evaluation_added = true;
+ }
+ }
+ }
+ // Enter the first result into the evaluator
  if let Some(reduced) = reduced {
  eval.try_image(Arc::new(reduced));
  evaluation_added = true;
  }
- if try_indexed && !deadline.passed() {
- if let Some(reduced) = indexed.and_then(|png| reduced_bit_depth_8_or_less(&png)) {
- eval.try_image(Arc::new(reduced));
- evaluation_added = true;
- }
- }
  }
 
  if evaluation_added {