graphic magic image transform

gistfile1.go

func resize(context *core.Context, imageWidth int, imageHeight int, quality string, destination string) error {
	reqWidth, reqHeight := context.Width, context.Height
	finalWidth, finalHeight := imageWidth, imageHeight
	var resizeArgument, extendArgument string

	if context.Width == 0 {
		resizeArgument = strconv.Itoa(finalWidth) + "x" + strconv.Itoa(finalHeight)
		extendArgument = "+0+0"
	} else {
		finalWidth, finalHeight = reqWidth, reqHeight
		widthRatio := float64(reqWidth) / float64(imageWidth)
		heightRatio := float64(reqHeight) / float64(imageHeight)
		ratio := widthRatio
		if context.Preserve {
			if heightRatio < widthRatio {
				ratio = heightRatio
			}
		} else {
			if heightRatio > widthRatio {
				ratio = heightRatio
			}
		}
		finalWidth = int(float64(imageWidth)*ratio) + 1
		finalHeight = int(float64(imageHeight)*ratio) + 1

		resizeArgument = strconv.Itoa(reqWidth) + "x" + strconv.Itoa(reqHeight)
		extendArgument = resizeArgument
		if context.Anchored {
			ax := float64(context.AnchorX) / float64(imageWidth) * float64(finalWidth-reqWidth)
			ay := float64(context.AnchorY) / float64(imageHeight) * float64(finalHeight-reqHeight)
			extendArgument += "+" + strconv.Itoa(int(ax)) + "+" + strconv.Itoa(int(ay))
		} else {
			extendArgument += "+" + strconv.Itoa(int(float64((finalWidth-reqWidth)/2.0))) + "+" + strconv.Itoa(int(float64((finalHeight-reqHeight)/2.0)))
		}
	}

	args := []string{
		"convert",
		"-size", resizeArgument,
		"-resize", strconv.Itoa(finalWidth) + "x" + strconv.Itoa(finalHeight),
		"-extent", extendArgument,
		"-quality", quality,
		"-strip",
		"-interlace", "line",
		context.OriginalPath,
		destination,
	}
	return exec.Command("gm", args...).Run()
}