fix: improve performance of png and webp

[styfle]

Disclosure - this was written by AI and modified by me.

Seeing up to 115x speed up for some of the test cases (regular.webp)

Toggle to view benchmark results

=== Real test files (static) ===

actl-chunk-after-fdat-chunks.png (521 bytes):
  old: 47.05ms total, 0.0005ms/op (100000 iterations)
  new: 44.38ms total, 0.0004ms/op (100000 iterations)
  speedup: 1.1x

idat-chunk-after-fdat-chunks.png (521 bytes):
  old: 45.87ms total, 0.0005ms/op (100000 iterations)
  new: 45.35ms total, 0.0005ms/op (100000 iterations)
  speedup: 1.0x

no-acTL-chunk.png (501 bytes):
  old: 37.89ms total, 0.0004ms/op (100000 iterations)
  new: 37.74ms total, 0.0004ms/op (100000 iterations)
  speedup: 1.0x

no-fcTL-chunk-before-IDAT-chunk.png (483 bytes):
  old: 40.50ms total, 0.0004ms/op (100000 iterations)
  new: 41.10ms total, 0.0004ms/op (100000 iterations)
  speedup: 1.0x

no-fcTL-chunks.png (407 bytes):
  old: 40.73ms total, 0.0004ms/op (100000 iterations)
  new: 40.55ms total, 0.0004ms/op (100000 iterations)
  speedup: 1.0x

no-fdAT-chunks.png (214 bytes):
  old: 56.69ms total, 0.0006ms/op (100000 iterations)
  new: 56.18ms total, 0.0006ms/op (100000 iterations)
  speedup: 1.0x

regular.gif (100 bytes):
  old: 22.10ms total, 0.0002ms/op (100000 iterations)
  new: 21.74ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

regular.png (156 bytes):
  old: 29.89ms total, 0.0003ms/op (100000 iterations)
  new: 30.46ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

regular.webp (10474 bytes):
  old: 1979.78ms total, 0.0198ms/op (100000 iterations)
  new: 17.12ms total, 0.0002ms/op (100000 iterations)
  speedup: 115.7x

with-comment-extension.gif (113 bytes):
  old: 23.54ms total, 0.0002ms/op (100000 iterations)
  new: 22.92ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

with-local-color-table.gif (106 bytes):
  old: 22.68ms total, 0.0002ms/op (100000 iterations)
  new: 25.99ms total, 0.0003ms/op (100000 iterations)
  speedup: 0.9x

with-plain-text-extension.gif (128 bytes):
  old: 24.42ms total, 0.0002ms/op (100000 iterations)
  new: 23.85ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

=== Real test files (invalid) ===

empty.gif (0 bytes):
  old: 7.52ms total, 0.0001ms/op (100000 iterations)
  new: 6.75ms total, 0.0001ms/op (100000 iterations)
  speedup: 1.1x

empty.webp (0 bytes):
  old: 5.50ms total, 0.0001ms/op (100000 iterations)
  new: 5.80ms total, 0.0001ms/op (100000 iterations)
  speedup: 0.9x

invalid-color-table-length.gif (216 bytes):
  old: 21.23ms total, 0.0002ms/op (100000 iterations)
  new: 20.91ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

invalid-header.gif (219 bytes):
  old: 15.26ms total, 0.0002ms/op (100000 iterations)
  new: 14.91ms total, 0.0001ms/op (100000 iterations)
  speedup: 1.0x

no-IDAT-chunk.png (372 bytes):
  old: 48.94ms total, 0.0005ms/op (100000 iterations)
  new: 48.99ms total, 0.0005ms/op (100000 iterations)
  speedup: 1.0x

=== Real test files (animated) ===

87a.gif (176 bytes):
  old: 22.36ms total, 0.0002ms/op (100000 iterations)
  new: 21.43ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

invalid-version.gif (219 bytes):
  old: 23.83ms total, 0.0002ms/op (100000 iterations)
  new: 23.77ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

no-fcTL-chunk-before-last-fdAT-chunk.png (483 bytes):
  old: 82.43ms total, 0.0008ms/op (100000 iterations)
  new: 64.72ms total, 0.0006ms/op (100000 iterations)
  speedup: 1.3x

no-graphic-control-extensions.gif (195 bytes):
  old: 23.50ms total, 0.0002ms/op (100000 iterations)
  new: 23.20ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

no-netscape-application-extension.gif (200 bytes):
  old: 23.68ms total, 0.0002ms/op (100000 iterations)
  new: 23.23ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

regular.gif (218 bytes):
  old: 24.50ms total, 0.0002ms/op (100000 iterations)
  new: 24.10ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

regular.png (521 bytes):
  old: 88.73ms total, 0.0009ms/op (100000 iterations)
  new: 60.80ms total, 0.0006ms/op (100000 iterations)
  speedup: 1.5x

regular.webp (41064 bytes):
  old: 23.66ms total, 0.0002ms/op (100000 iterations)
  new: 16.86ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.4x

truncated-inside-second-frame.gif (151 bytes):
  old: 26.12ms total, 0.0003ms/op (100000 iterations)
  new: 26.68ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

truncated-inside-third-frame.gif (181 bytes):
  old: 25.14ms total, 0.0003ms/op (100000 iterations)
  new: 25.41ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

with-comment-extension.gif (232 bytes):
  old: 25.76ms total, 0.0003ms/op (100000 iterations)
  new: 25.96ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

with-empty-frames.gif (124 bytes):
  old: 24.83ms total, 0.0002ms/op (100000 iterations)
  new: 25.11ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

with-local-color-table.gif (225 bytes):
  old: 25.51ms total, 0.0003ms/op (100000 iterations)
  new: 25.56ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

with-plain-text-extension.gif (247 bytes):
  old: 25.88ms total, 0.0003ms/op (100000 iterations)
  new: 26.12ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

without-color-table.gif (195 bytes):
  old: 18.05ms total, 0.0002ms/op (100000 iterations)
  new: 18.13ms total, 0.0002ms/op (100000 iterations)
  speedup: 1.0x

zero-delays.gif (219 bytes):
  old: 25.10ms total, 0.0003ms/op (100000 iterations)
  new: 25.27ms total, 0.0003ms/op (100000 iterations)
  speedup: 1.0x

[styfle]

@qzb Thoughts?