A-M baby

Task/Image-convolution/Go/image-convolution-1.go

@@ -0,0 +1,91 @@
+package main
+
+import (
+    "fmt"
+    "image"
+    "image/color"
+    "image/jpeg"
+    "math"
+    "os"
+)
+
+// kf3 is a generic convolution 3x3 kernel filter that operatates on
+// images of type image.Gray from the Go standard image library.
+func kf3(k *[9]float64, src, dst *image.Gray) {
+    for y := src.Rect.Min.Y; y < src.Rect.Max.Y; y++ {
+        for x := src.Rect.Min.X; x < src.Rect.Max.X; x++ {
+            var sum float64
+            var i int
+            for yo := y - 1; yo <= y+1; yo++ {
+                for xo := x - 1; xo <= x+1; xo++ {
+                    if (image.Point{xo, yo}).In(src.Rect) {
+                        sum += k[i] * float64(src.At(xo, yo).(color.Gray).Y)
+                    } else {
+                        sum += k[i] * float64(src.At(x, y).(color.Gray).Y)
+                    }
+                    i++
+                }
+            }
+            dst.SetGray(x, y,
+                color.Gray{uint8(math.Min(255, math.Max(0, sum)))})
+        }
+    }
+}
+
+var blur = [9]float64{
+    1. / 9, 1. / 9, 1. / 9,
+    1. / 9, 1. / 9, 1. / 9,
+    1. / 9, 1. / 9, 1. / 9}
+
+// blurY example function applies blur kernel to Y channel
+// of YCbCr image using generic kernel filter function kf3
+func blurY(src *image.YCbCr) *image.YCbCr {
+    dst := *src
+
+    // catch zero-size image here
+    if src.Rect.Max.X == src.Rect.Min.X || src.Rect.Max.Y == src.Rect.Min.Y {
+        return &dst
+    }
+
+    // pass Y channels as gray images
+    srcGray := image.Gray{src.Y, src.YStride, src.Rect}
+    dstGray := srcGray
+    dstGray.Pix = make([]uint8, len(src.Y))
+    kf3(&blur, &srcGray, &dstGray) // call generic convolution function
+
+    // complete result
+    dst.Y = dstGray.Pix                   // convolution result
+    dst.Cb = append([]uint8{}, src.Cb...) // Cb, Cr are just copied
+    dst.Cr = append([]uint8{}, src.Cr...)
+    return &dst
+}
+
+func main() {
+    // Example file used here is Lenna100.jpg from the task "Percentage
+    // difference between images"
+    f, err := os.Open("Lenna100.jpg")
+    if err != nil {
+        fmt.Println(err)
+        return
+    }
+    img, err := jpeg.Decode(f)
+    if err != nil {
+        fmt.Println(err)
+        return
+    }
+    f.Close()
+    y, ok := img.(*image.YCbCr)
+    if !ok {
+        fmt.Println("expected color jpeg")
+        return
+    }
+    f, err = os.Create("blur.jpg")
+    if err != nil {
+        fmt.Println(err)
+        return
+    }
+    err = jpeg.Encode(f, blurY(y), &jpeg.Options{90})
+    if err != nil {
+        fmt.Println(err)
+    }
+}