thumbnail/image.go

package thumbnail

import (
	"image"

	"code.ivysaur.me/imagequant"
)

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)

		}
	}

	return crush(dest, imagequant.SPEED_FASTEST)
}