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add lower level png decoding api

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This commit is contained in:
Ryan Oldenburg 2021-09-01 16:23:44 -05:00
parent e06e13b2ce
commit 5a691153a1
1 changed files with 18 additions and 7 deletions
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25
src/pixie/fileformats/png.nim
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@ -14,6 +14,10 @@ type
width, height: int
bitDepth, colorType, compressionMethod, filterMethod, interlaceMethod: uint8
Png* = ref object
width*, height*, channels*: int
data*: seq[ColorRGBA]
template failInvalid() =
raise newException(PixieError, "Invalid PNG buffer, unable to load")
@ -316,9 +320,8 @@ proc decodeImageData(
else:
discard # Not possible, parseHeader validates
proc decodePng*(data: string): Image {.raises: [PixieError].} =
## Decodes the PNG data into an Image.
proc decodePngRaw*(data: string): Png {.raises: [PixieError].} =
## Decodes the PNG data.
if data.len < (8 + (8 + 13 + 4) + 4): # Magic bytes + IHDR + IEND
failInvalid()
@ -420,11 +423,19 @@ proc decodePng*(data: string): Image {.raises: [PixieError].} =
if prevChunkType != "IEND":
failInvalid()
var pixels = decodeImageData(header, palette, transparency, imageData)
pixels.toPremultipliedAlpha()
result = Png()
result.width = header.width
result.height = header.height
result.channels = 4
result.data = decodeImageData(header, palette, transparency, imageData)
result = newImage(header.width, header.height)
copyMem(result.data[0].addr, pixels[0].addr, pixels.len * 4)
proc decodePng*(data: string): Image {.raises: [PixieError].} =
## Decodes the PNG data into an Image.
let png = decodePngRaw(data)
png.data.toPremultipliedAlpha()
result = newImage(png.width, png.height)
copyMem(result.data[0].addr, png.data[0].addr, png.data.len * 4)
proc encodePng*(
width, height, channels: int, data: pointer, len: int