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image.go
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/
image.go
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package pigo
import (
"image"
"image/color"
_ "image/jpeg"
_ "image/png"
"os"
)
// GetImage retrieves and decodes the image file to *image.NRGBA type.
func GetImage(input string) (*image.NRGBA, error) {
file, err := os.Open(input)
if err != nil {
return nil, err
}
defer file.Close()
src, _, err := image.Decode(file)
if err != nil {
return nil, err
}
img := ImgToNRGBA(src)
return img, nil
}
// ImgToNRGBA converts any image type to *image.NRGBA with min-point at (0, 0).
func ImgToNRGBA(img image.Image) *image.NRGBA {
srcBounds := img.Bounds()
if srcBounds.Min.X == 0 && srcBounds.Min.Y == 0 {
if src0, ok := img.(*image.NRGBA); ok {
return src0
}
}
srcMinX := srcBounds.Min.X
srcMinY := srcBounds.Min.Y
dstBounds := srcBounds.Sub(srcBounds.Min)
dstW := dstBounds.Dx()
dstH := dstBounds.Dy()
dst := image.NewNRGBA(dstBounds)
switch src := img.(type) {
case *image.NRGBA:
rowSize := srcBounds.Dx() * 4
for dstY := 0; dstY < dstH; dstY++ {
di := dst.PixOffset(0, dstY)
si := src.PixOffset(srcMinX, srcMinY+dstY)
for dstX := 0; dstX < dstW; dstX++ {
copy(dst.Pix[di:di+rowSize], src.Pix[si:si+rowSize])
}
}
case *image.YCbCr:
for dstY := 0; dstY < dstH; dstY++ {
di := dst.PixOffset(0, dstY)
for dstX := 0; dstX < dstW; dstX++ {
srcX := srcMinX + dstX
srcY := srcMinY + dstY
siy := src.YOffset(srcX, srcY)
sic := src.COffset(srcX, srcY)
r, g, b := color.YCbCrToRGB(src.Y[siy], src.Cb[sic], src.Cr[sic])
dst.Pix[di+0] = r
dst.Pix[di+1] = g
dst.Pix[di+2] = b
dst.Pix[di+3] = 0xff
di += 4
}
}
default:
for dstY := 0; dstY < dstH; dstY++ {
di := dst.PixOffset(0, dstY)
for dstX := 0; dstX < dstW; dstX++ {
c := color.NRGBAModel.Convert(img.At(srcMinX+dstX, srcMinY+dstY)).(color.NRGBA)
dst.Pix[di+0] = c.R
dst.Pix[di+1] = c.G
dst.Pix[di+2] = c.B
dst.Pix[di+3] = c.A
di += 4
}
}
}
return dst
}