cmd

cmd/negate/negate.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"image"
+	"image/color"
+	"image/png"
+	"os"
+)
+
+func NegateRGBA(c color.RGBA) color.RGBA {
+	c.R = 255 - c.R
+	c.G = 255 - c.G
+	c.B = 255 - c.B
+	return c
+}
+
+type Negate struct{ image.Image }
+
+func (n Negate) ColorModel() color.Model { return n.Image.ColorModel() }
+func (n Negate) Bounds() image.Rectangle { return n.Image.Bounds() }
+func (n Negate) At(x, y int) color.Color {
+	c := n.Image.At(x, y)
+	r, g, b, a := c.RGBA()
+	RGBAColor := color.RGBA{
+		R: uint8(r >> 8),
+		G: uint8(g >> 8),
+		B: uint8(b >> 8),
+		A: uint8(a >> 8),
+	}
+	return NegateRGBA(RGBAColor)
+}
+
+func check(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	img, err := png.Decode(os.Stdin)
+	check(err)
+	err = png.Encode(os.Stdout, Negate{img})
+	check(err)
+}