Read more bmp formats.
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treeform
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3 changed files with 194 additions and 20 deletions
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@ -1,6 +1,9 @@
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import bitops, chroma, flatty/binny, pixie/common, pixie/images
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import print, strutils
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# See: https://en.wikipedia.org/wiki/BMP_file_format
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# See: https://bmptestsuite.sourceforge.io/
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const bmpSignature* = "BM"
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@ -10,64 +13,192 @@ proc colorMaskShift(color: uint32, mask: uint32): uint8 =
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proc decodeBmp*(data: string): Image {.raises: [PixieError].} =
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## Decodes bitmap data into an Image.
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if data.len < 48:
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raise newException(PixieError, "Invalid BMP data")
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# BMP Header
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if data[0 .. 1] != "BM":
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raise newException(PixieError, "Invalid BMP data")
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let
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width = data.readInt32(18).int
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height = data.readInt32(22).int
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bits = data.readUint16(28).int
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compression = data.readUint32(30).int
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dibHeader = data.readInt32(14).int
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var
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numColors = data.readInt32(46).int
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width = data.readInt32(18).int
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height = data.readInt32(22).int
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offset = data.readUInt32(10).int
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# Default channels if header does not contain them:
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redChannel = 0x00FF0000.uint32
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greenChannel = 0x0000FF00.uint32
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blueChannel = 0x000000FF.uint32
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alphaChannel = 0xFF000000.uint32
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useAlpha = false
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flipVertical = false
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if numColors < 0:
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raise newException(PixieError, "Invalid BMP data")
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if dibHeader notin [40, 108]:
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raise newException(PixieError, "Invalid BMP data")
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var
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colorTable = newSeq[ColorRGBA](numColors)
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if dibHeader == 108:
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if data.len < 14 + dibHeader:
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raise newException(PixieError, "Invalid BMP data")
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redChannel = data.readUInt32(54)
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greenChannel = data.readUInt32(58)
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blueChannel = data.readUInt32(62)
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alphaChannel = data.readUInt32(66)
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useAlpha = true
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if bits == 8 and numColors == 0:
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numColors = 256
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colorTable = newSeq[ColorRGBA](numColors)
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if numColors > 0:
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if data.len < 14 + dibHeader + numColors * 4:
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raise newException(PixieError, "Invalid BMP data")
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var colorOffset = dibHeader + 14
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for i in 0 ..< numColors:
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var rgba: ColorRGBA
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if colorOffset + 3 > data.len - 2:
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raise newException(PixieError, "Truncated BMP data")
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rgba.r = data.readUint8(colorOffset + 2)
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rgba.g = data.readUint8(colorOffset + 1)
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rgba.b = data.readUint8(colorOffset + 0)
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rgba.a = 255
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colorOffset += 4
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colorTable[i] = rgba
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if redChannel == 0 or greenChannel == 0 or
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blueChannel == 0 or alphaChannel == 0:
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raise newException(PixieError, "Unsupported 0 channel mask.")
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if bits notin [32, 24]:
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if bits notin [1, 4, 8, 32, 24]:
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raise newException(PixieError, "Unsupported BMP data format")
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if compression notin [0, 3]:
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raise newException(PixieError, "Unsupported BMP data format")
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let channels = if bits == 32: 4 else: 3
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if width * height * channels + offset > data.len:
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raise newException(PixieError, "Invalid BMP data size")
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if height < 0:
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height = -height
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flipVertical = true
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result = newImage(width, height)
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let startOffset = offset
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for y in 0 ..< result.height:
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for x in 0 ..< result.width:
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var rgba: ColorRGBA
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if bits == 32:
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let color = data.readUint32(offset)
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rgba.r = color.colorMaskShift(redChannel)
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rgba.g = color.colorMaskShift(greenChannel)
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rgba.b = color.colorMaskShift(blueChannel)
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rgba.a = color.colorMaskShift(alphaChannel)
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offset += 4
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elif bits == 24:
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if bits == 1:
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var
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haveBits = 0
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colorBits: uint8 = 0
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for y in 0 ..< result.height:
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# pad the row
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haveBits = 0
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let padding = (offset - startOffset) mod 4
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if padding > 0:
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offset += 4 - padding
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for x in 0 ..< result.width:
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if offset >= data.len:
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raise newException(PixieError, "Truncated BMP data")
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var rgba: ColorRGBA
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if haveBits == 0:
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colorBits = data.readUint8(offset)
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haveBits = 8
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offset += 1
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if (colorBits and 0b1000_0000) == 0:
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rgba = colorTable[0]
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else:
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rgba = colorTable[1]
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colorBits = colorBits shl 1
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dec haveBits
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result[x, result.height - y - 1] = rgba.rgbx()
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elif bits == 4:
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var
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haveBits = 0
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colorBits: uint8 = 0
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for y in 0 ..< result.height:
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# pad the row
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haveBits = 0
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let padding = (offset - startOffset) mod 4
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if padding > 0:
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offset += 4 - padding
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for x in 0 ..< result.width:
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if offset >= data.len:
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raise newException(PixieError, "Truncated BMP data")
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var rgba: ColorRGBA
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if haveBits == 0:
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colorBits = data.readUint8(offset)
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haveBits = 8
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offset += 1
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let index = (colorBits and 0b1111_0000) shr 4
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if index.int >= numColors:
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raise newException(PixieError, "Invalid BMP index")
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rgba = colorTable[index]
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colorBits = colorBits shl 4
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haveBits -= 4
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result[x, result.height - y - 1] = rgba.rgbx()
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elif bits == 8:
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for y in 0 ..< result.height:
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# pad the row
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let padding = (offset - startOffset) mod 4
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if padding > 0:
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offset += 4 - padding
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for x in 0 ..< result.width:
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if offset >= data.len:
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raise newException(PixieError, "Truncated BMP data")
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var rgba: ColorRGBA
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let index = data.readUint8(offset)
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offset += 1
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if index.int >= numColors:
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raise newException(PixieError, "Invalid BMP index")
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rgba = colorTable[index]
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result[x, result.height - y - 1] = rgba.rgbx()
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elif bits == 24:
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for y in 0 ..< result.height:
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# pad the row
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let padding = (offset - startOffset) mod 4
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if padding >= 0:
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offset += 4 - padding
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for x in 0 ..< result.width:
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if offset + 3 > data.len:
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raise newException(PixieError, "Truncated BMP data")
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var rgba: ColorRGBA
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rgba.r = data.readUint8(offset + 2)
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rgba.g = data.readUint8(offset + 1)
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rgba.b = data.readUint8(offset + 0)
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rgba.a = 255
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offset += 3
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result[x, result.height - y - 1] = rgba.rgbx()
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result[x, result.height - y - 1] = rgba.rgbx()
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if bits == 32:
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for y in 0 ..< result.height:
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for x in 0 ..< result.width:
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if offset >= data.len - 2:
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raise newException(PixieError, "Truncated BMP data")
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var rgba: ColorRGBA
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let color = data.readUint32(offset)
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rgba.r = color.colorMaskShift(redChannel)
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rgba.g = color.colorMaskShift(greenChannel)
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rgba.b = color.colorMaskShift(blueChannel)
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if useAlpha:
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rgba.a = color.colorMaskShift(alphaChannel)
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else:
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rgba.a = 255
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offset += 4
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result[x, result.height - y - 1] = rgba.rgbx()
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if flipVertical:
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result.flipVertical()
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proc decodeBmp*(data: seq[uint8]): Image {.inline, raises: [PixieError].} =
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## Decodes bitmap data into an Image.
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38
tests/fuzz_bmp.nim
Normal file
38
tests/fuzz_bmp.nim
Normal file
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@ -0,0 +1,38 @@
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import pixie/common, pixie/fileformats/bmp, random, strformat, flatty/binny, os
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randomize()
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var originals = @[readFile("tests/fileformats/bmp/knight.32.bmp")]
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for file in walkFiles("tests/fileformats/bmp/bmpsuite/*"):
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originals.add(readFile(file))
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for i in 0 ..< 100_000:
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var data = originals[rand(originals.len-1)]
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let
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pos = rand(data.len-1)
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value = rand(255).char
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# pos = 27355
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# value = '&'
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data[pos] = value
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let
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width = data.readInt32(18).int
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height = data.readInt32(22).int
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numColors = data.readInt32(46).int
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if abs(width) > 1000 or abs(height) > 1000 or numColors > 1000:
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echo "too big"
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continue
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echo &"{i} {pos} {repr(value)}"
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try:
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let img = decodeBmp(data)
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doAssert img.height > 0 and img.width > 0
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except PixieError:
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discard
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data = data[0 ..< pos]
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try:
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let img = decodeBmp(data)
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doAssert img.height > 0 and img.width > 0
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except PixieError:
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discard
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@ -1,4 +1,4 @@
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import chroma, pixie, pixie/fileformats/bmp
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import chroma, pixie, pixie/fileformats/bmp, os, strutils
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# block:
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# var image = newImage(4, 2)
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@ -42,3 +42,8 @@ block:
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"tests/fileformats/bmp/rgb.24.master.bmp"
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))
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writeFile("tests/fileformats/bmp/rgb.24.bmp", encodeBmp(image))
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block:
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for file in walkFiles("tests/fileformats/bmp/bmpsuite/*"):
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let image = decodeBmp(readFile(file))
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image.writeFile(file.replace("bmpsuite", "output") & ".png")
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