wasm: added image/pixel conversion utility package

pixels/image.go

@@ -0,0 +1,55 @@
+package pixels
+
+import (
+	"image"
+	"image/color"
+	"math"
+)
+
+// ImgToPix converts an image to pixel data.
+func ImgToPix(img image.Image) []uint8 {
+	bounds := img.Bounds()
+	pixels := make([]uint8, 0, bounds.Max.X*bounds.Max.Y*4)
+
+	for i := bounds.Min.X; i < bounds.Max.X; i++ {
+		for j := bounds.Min.Y; j < bounds.Max.Y; j++ {
+			r, g, b, _ := img.At(i, j).RGBA()
+			pixels = append(pixels, uint8(r>>8), uint8(g>>8), uint8(b>>8), 255)
+		}
+	}
+	return pixels
+}
+
+// PixToImage converts the pixel data to an image.
+func PixToImage(pixels []uint8, dim int) image.Image {
+	img := image.NewNRGBA(image.Rect(0, 0, dim, dim))
+	bounds := img.Bounds()
+	dx, dy := bounds.Max.X, bounds.Max.Y
+	col := color.NRGBA{}
+
+	for y := bounds.Min.Y; y < dy; y++ {
+		for x := bounds.Min.X; x < dx*4; x += 4 {
+			col.R = pixels[x+y*dx*4]
+			col.G = pixels[x+y*dx*4+1]
+			col.B = pixels[x+y*dx*4+2]
+			col.A = pixels[x+y*dx*4+3]
+
+			img.SetNRGBA(y, int(x/4), col)
+		}
+	}
+	return img
+}
+
+// RgbaToGrayscale converts the pixel data to grayscale mode.
+func RgbaToGrayscale(data []uint8, dx, dy int) []uint8 {
+	for r := 0; r < dx; r++ {
+		for c := 0; c < dy; c++ {
+			// gray = 0.2*red + 0.7*green + 0.1*blue
+			data[r*dy+c] = uint8(math.Round(
+				0.2126*float64(data[r*4*dy+4*c+0]) +
+					0.7152*float64(data[r*4*dy+4*c+1]) +
+					0.0722*float64(data[r*4*dy+4*c+2])))
+		}
+	}
+	return data
+}