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image: modify QOI to allow for loading from []byte #1

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image: modify QOI to allow for loading from []byte #1

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26 changes: 25 additions & 1 deletion image/qoi.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ import (
//
// For more information, see: https://qoiformat.org/
type QOI[T pixel.Color] struct {
data string
data []byte
width, height int
state qoiDecodeState[T]
}
Expand Down Expand Up @@ -48,6 +48,30 @@ func NewQOI[T pixel.Color](data string) (*QOI[T], error) {
// The colorspace affects how a pixel.Color is encoded.
return nil, errQOIUnsupportedColorSpace
}
img := &QOI[T]{
data: []byte(data),
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@aykevl aykevl Mar 9, 2024

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This will result in a heap allocation the size of the image, which is probably not what you want.
We could unsafely cast the string to a byte slice using unsafe.Slice (and then make sure to never modify it) to avoid this. It's a bit dangerous though.

}
img.width = int(uint32(data[4])<<24 | uint32(data[5])<<16 | uint32(data[6])<<8 | uint32(data[7])<<0)
img.height = int(uint32(data[8])<<24 | uint32(data[9])<<16 | uint32(data[10])<<8 | uint32(data[11])<<0)
img.state.reset()
return img, nil
}

func NewQOIFromBytes[T pixel.Color](data []byte) (*QOI[T], error) {
if len(data) < 14 {
return nil, errQOIHeaderTooSmall
}
if string(data[:4]) != "qoif" {
return nil, errQOIInvalidMagic
}
if data[12] != 3 {
// We only support RGB, we don't support the alpha channel (yet!).
return nil, errQOIUnsupportedChannelNum
}
if data[13] != qoiColorSpaceSRGB {
// The colorspace affects how a pixel.Color is encoded.
return nil, errQOIUnsupportedColorSpace
}
img := &QOI[T]{
data: data,
}
Expand Down