grokify/mogo

package imageutil

import (
    "image"
    "image/color"
    "image/color/palette"
    "image/draw"
)

func ImageToPaletted(src image.Image, p color.Palette) *image.Paletted {
    if dst, ok := src.(*image.Paletted); ok {
        return dst
    }
    dst := image.NewPaletted(src.Bounds(), p)
    draw.Draw(dst, dst.Rect, src, src.Bounds().Min, draw.Over)
    return dst
}

type ToPalettedFunc func(src image.Image) *image.Paletted

// ImageToPalettedPlan9 converts an image to `*image.Paletted`. See the
// go implementation here: https://github.com/golang/go/blob/master/src/image/gif/writer.go
func ImageToPalettedPlan9(src image.Image) *image.Paletted {
    return ImageToPaletted(src, palette.Plan9)
}

// ImageToPalettedWebSafe uses the 216 color palete created by Netscape.
// See more here: https://en.wikipedia.org/wiki/Web_colors#Web-safe_colors
func ImageToPalettedWebSafe(src image.Image) *image.Paletted {
    return ImageToPaletted(src, palette.WebSafe)
}

func ImageToRGBA(src image.Image) *image.RGBA {
    /*
        // https://stackoverflow.com/questions/31463756/convert-image-image-to-image-nrgba
        switch img := img.(type) {
        case *image.NRGBA:
            return NRGBAtoRGBA(img)
        case *image.Paletted:
            return ImageWithSetToRGBA(img)
        case *image.YCbCr:
            return YCbCrToRGBA(img)
        }
    */
    if dst, ok := src.(*image.RGBA); ok {
        return dst
    }
    b := src.Bounds()
    dst := image.NewRGBA(image.Rect(0, 0, b.Dx(), b.Dy()))
    draw.Draw(dst, dst.Rect, src, src.Bounds().Min, draw.Src)
    return dst
}

/*
func ImageWithSetToRGBA(src draw.Image) *image.RGBA {
    rect := src.Bounds()
    imgRGBA := image.NewRGBA(rect)
    for x := rect.Min.X; x <= rect.Max.X; x++ {
        for y := rect.Min.Y; y <= rect.Max.Y; y++ {
            imgRGBA.Set(x, y, src.At(x, y))
        }
    }
    return imgRGBA
}

func NRGBAtoRGBA(imgNRGBA *image.NRGBA) *image.RGBA {
    rect := imgNRGBA.Bounds()
    imgRGBA := image.NewRGBA(rect)
    for x := rect.Min.X; x <= rect.Max.X; x++ {
        for y := rect.Min.Y; y <= rect.Max.Y; y++ {
            imgRGBA.Set(x, y, imgNRGBA.At(x, y))
        }
    }
    return imgRGBA
}

func YCbCrToRGBA(src *image.YCbCr) *image.RGBA {
    // https://stackoverflow.com/questions/31463756/convert-image-image-to-image-nrgba
    b := src.Bounds()
    img := image.NewRGBA(image.Rect(0, 0, b.Dx(), b.Dy()))
    draw.Draw(img, img.Bounds(), src, b.Min, draw.Src)
    return img
}
*/