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png decode perf improvement

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Ryan Oldenburg 2021-04-11 13:09:16 -05:00
parent 75915ab05f
commit 8dbb78c387
1 changed files with 26 additions and 16 deletions
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42
src/pixie/fileformats/png.nim
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@ -102,33 +102,44 @@ proc unfilter(
# Unfilter the image data # Unfilter the image data
for y in 0 ..< height: for y in 0 ..< height:
let filterType = uncompressed[uncompressedIdx(0, y)] let filterType = uncompressed[uncompressedIdx(0, y)]
for x in 0 ..< rowBytes: case filterType:
var value = uncompressed[uncompressedIdx(x + 1, y)] of 0: # None
case filterType: discard
of 0: # None of 1: # Sub
discard for x in 0 ..< rowBytes:
of 1: # Sub var value = uncompressed[uncompressedIdx(x + 1, y)]
if x - bpp >= 0: if x - bpp >= 0:
value += result[unfiteredIdx(x - bpp, y)] value += result[unfiteredIdx(x - bpp, y)]
of 2: # Up result[unfiteredIdx(x, y)] = value
of 2: # Up
for x in 0 ..< rowBytes:
var value = uncompressed[uncompressedIdx(x + 1, y)]
if y - 1 >= 0: if y - 1 >= 0:
value += result[unfiteredIdx(x, y - 1)] value += result[unfiteredIdx(x, y - 1)]
of 3: # Average result[unfiteredIdx(x, y)] = value
var left, up: int of 3: # Average
for x in 0 ..< rowBytes:
var
value = uncompressed[uncompressedIdx(x + 1, y)]
left, up: int
if x - bpp >= 0: if x - bpp >= 0:
left = result[unfiteredIdx(x - bpp, y)].int left = result[unfiteredIdx(x - bpp, y)].int
if y - 1 >= 0: if y - 1 >= 0:
up = result[unfiteredIdx(x, y - 1)].int up = result[unfiteredIdx(x, y - 1)].int
value += ((left + up) div 2).uint8 value += ((left + up) div 2).uint8
of 4: # Paeth result[unfiteredIdx(x, y)] = value
var left, up, upLeft: int of 4: # Paeth
for x in 0 ..< rowBytes:
var
value = uncompressed[uncompressedIdx(x + 1, y)]
left, up, upLeft: int
if x - bpp >= 0: if x - bpp >= 0:
left = result[unfiteredIdx(x - bpp, y)].int left = result[unfiteredIdx(x - bpp, y)].int
if y - 1 >= 0: if y - 1 >= 0:
up = result[unfiteredIdx(x, y - 1)].int up = result[unfiteredIdx(x, y - 1)].int
if x - bpp >= 0 and y - 1 >= 0: if x - bpp >= 0 and y - 1 >= 0:
upLeft = result[unfiteredIdx(x - bpp, y - 1)].int upLeft = result[unfiteredIdx(x - bpp, y - 1)].int
proc paethPredictor(a, b, c: int): int {.inline.} = template paethPredictor(a, b, c: int): int =
let let
p = a + b - c p = a + b - c
pa = abs(p - a) pa = abs(p - a)
@ -141,10 +152,9 @@ proc unfilter(
else: else:
c c
value += paethPredictor(up, left, upLeft).uint8 value += paethPredictor(up, left, upLeft).uint8
else: result[unfiteredIdx(x, y)] = value
discard # Not possible, parseHeader validates else:
discard # Not possible, parseHeader validates
result[unfiteredIdx(x, y)] = value
proc decodeImageData( proc decodeImageData(
header: PngHeader, header: PngHeader,