thumbnail/image.go

99 lines
2.1 KiB
Go

package thumbnail
import (
"image"
"image/color"
)
func Blend(a, b color.Color) color.Color {
switch a.(type) {
case color.RGBA:
return BlendRGBA(a.(color.RGBA), b.(color.RGBA)) // FIXME there's syntax for this
case color.YCbCr:
return BlendYCbCr(a.(color.YCbCr), b.(color.YCbCr))
default:
return a // ??? unknown color format
}
}
func BlendYCbCr(a, b color.YCbCr) color.YCbCr {
return color.YCbCr{
Y: uint8((int(a.Y) + int(b.Y)) / 2),
Cb: uint8((int(a.Cb) + int(b.Cb)) / 2),
Cr: uint8((int(a.Cr) + int(b.Cr)) / 2),
}
}
func BlendRGBA(a, b color.RGBA) color.RGBA {
return color.RGBA{
R: uint8((int(a.R) + int(b.R)) / 2),
G: uint8((int(a.G) + int(b.G)) / 2),
B: uint8((int(a.B) + int(b.B)) / 2),
A: uint8((int(a.A) + int(b.A)) / 2),
}
}
func (this *Thumbnailer) RenderScaledImage(src image.Image) ([]byte, error) {
srcW := src.Bounds().Max.X
srcH := src.Bounds().Max.Y
destW := 0
destH := 0
if srcW > srcH {
destW = this.Width
destH = this.Height * srcH / srcW
} else {
destW = this.Width * srcW / srcH
destH = this.Height
}
offsetX := (this.Width - destW) / 2
offsetY := (this.Height - destH) / 2
scaleW := float64(srcW) / float64(destW)
scaleH := float64(srcH) / float64(destH)
dest := image.NewRGBA(image.Rectangle{Max: image.Point{X: this.Width, Y: this.Height}})
for y := 0; y < destH; y += 1 {
for x := 0; x < destW; x += 1 {
/*
// NN
mapx := int(float64(x) * scaleW)
mapy := int(float64(y) * scaleH)
dest.Set(x+offsetX, y+offsetY, src.At(mapx, mapy))
*/
// Bilinear
c00 := src.At(int(float64(x)*scaleW), int(float64(y)*scaleH))
c01 := src.At(int((float64(x)+0.5)*scaleW), int(float64(y)*scaleH))
c10 := src.At(int(float64(x)*scaleW), int((float64(y)+0.5)*scaleH))
c11 := src.At(int((float64(x)+0.5)*scaleW), int((float64(y)+0.5)*scaleH))
cBlend := Blend(Blend(c00, c01), Blend(c10, c11))
dest.Set(x+offsetX, y+offsetY, cBlend)
}
}
/*var b bytes.Buffer*/
return crush(dest, 3)
/*
err := png.Encode(&b, dest)
if err != nil {
return nil, err
}
*/
/*
err := jpeg.Encode(&b, dest, nil)
if err != nil {
return nil, err
}
return b.Bytes(), nil*/
}