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copied!<p>I had this problem myself and came up with a slightly different solution. I introduced a new type, <code>Converted</code>, which implements <code>image.Image</code>. <code>Converted</code> consists of the original image and the <code>color.Model</code>.</p> <p><code>Converted</code> does the conversion every time it is accessed, which could give slightly worse performance, but on the other hand it is cool and composable. </p> <pre><code>package main import ( "image" _ "image/jpeg" // Register JPEG format "image/png" // Register PNG format "image/color" "log" "os" ) // Converted implements image.Image, so you can // pretend that it is the converted image. type Converted struct { Img image.Image Mod color.Model } // We return the new color model... func (c *Converted) ColorModel() color.Model{ return c.Mod } // ... but the original bounds func (c *Converted) Bounds() image.Rectangle{ return c.Img.Bounds() } // At forwards the call to the original image and // then asks the color model to convert it. func (c *Converted) At(x, y int) color.Color{ return c.Mod.Convert(c.Img.At(x,y)) } func main() { if len(os.Args) != 3 { log.Fatalln("Needs two arguments")} infile, err := os.Open(os.Args[1]) if err != nil { log.Fatalln(err) } defer infile.Close() img, _, err := image.Decode(infile) if err != nil { log.Fatalln(err) } // Since Converted implements image, this is now a grayscale image gr := &Converted{img, color.GrayModel} // Or do something like this to convert it into a black and // white image. // bw := []color.Color{color.Black,color.White} // gr := &Converted{img, color.Palette(bw)} outfile, err := os.Create(os.Args[2]) if err != nil { log.Fatalln(err) } defer outfile.Close() png.Encode(outfile,gr) } </code></pre>

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