first commit

tools/alphaprobe/main.go

@@ -0,0 +1,77 @@
+// alphaprobe：打印一张图若干采样点的 RGBA，并统计 alpha 分布。
+//
+// 用来诊断「缩放后图标看起来全透明」这类问题 ——
+// 光看缩略图分不清是图像真透明，还是预览器把透明当白底。
+//
+// 用法：go run ./tools/alphaprobe <img.png> [更多.png...]
+package main
+
+import (
+	"fmt"
+	"image"
+	"image/png"
+	"os"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Fprintln(os.Stderr, "用法: go run ./tools/alphaprobe <img>...")
+		os.Exit(1)
+	}
+	for _, p := range os.Args[1:] {
+		probe(p)
+		fmt.Println()
+	}
+}
+
+func probe(path string) {
+	f, err := os.Open(path)
+	if err != nil {
+		fmt.Printf("%s: %v\n", path, err)
+		return
+	}
+	defer f.Close()
+
+	im, err := png.Decode(f)
+	if err != nil {
+		fmt.Printf("%s: 解不开: %v\n", path, err)
+		return
+	}
+	b := im.Bounds()
+	fmt.Printf("%s  bounds=%v\n", path, b)
+
+	pts := []struct {
+		name string
+		x, y int
+	}{
+		{"左上角", b.Min.X, b.Min.Y},
+		{"中心", b.Min.X + b.Dx()/2, b.Min.Y + b.Dy()/2},
+		{"上边中", b.Min.X + b.Dx()/2, b.Min.Y},
+		{"左边中", b.Min.X, b.Min.Y + b.Dy()/2},
+		{"右下角", b.Max.X - 1, b.Max.Y - 1},
+	}
+	for _, p := range pts {
+		r, g, bl, a := im.At(p.x, p.y).RGBA()
+		fmt.Printf("  %-8s (%3d,%3d)  R=%3d G=%3d B=%3d A=%3d\n",
+			p.name, p.x, p.y, r>>8, g>>8, bl>>8, a>>8)
+	}
+
+	var opaque, semi, clear int
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			if _, _, _, a := im.At(x, y).RGBA(); a>>8 > 240 {
+				opaque++
+			} else if a>>8 > 10 {
+				semi++
+			} else {
+				clear++
+			}
+		}
+	}
+	total := b.Dx() * b.Dy()
+	fmt.Printf("  alpha: 不透明 %d (%.1f%%) · 半透明 %d (%.1f%%) · 透明 %d (%.1f%%)\n",
+		opaque, 100*float64(opaque)/float64(total),
+		semi, 100*float64(semi)/float64(total),
+		clear, 100*float64(clear)/float64(total))
+	_ = image.Rect
+}