feat: Windows (CF_DIB) and macOS (AppleScript) clipboard image sync

internal/clipboard/dib_windows.go

@@ -0,0 +1,118 @@
+//go:build windows
+
+package clipboard
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"image"
+	"image/color"
+	"image/png"
+)
+
+const (
+	biRGB         = 0
+	cfDIB         = 8
+	dibHeaderSize = 40
+)
+
+// pngToDIB converts a PNG image to a 32bpp bottom-up BI_RGB DIB. The DIB layout
+// is BITMAPINFOHEADER (40 bytes) followed by tightly packed BGRA rows, which is
+// the form Windows expects for the CF_DIB clipboard format.
+func pngToDIB(pngData []byte) ([]byte, error) {
+	img, err := png.Decode(bytes.NewReader(pngData))
+	if err != nil {
+		return nil, err
+	}
+	b := img.Bounds()
+	w, h := b.Dx(), b.Dy()
+
+	dib := make([]byte, dibHeaderSize+w*4*h)
+
+	le := binary.LittleEndian
+	le.PutUint32(dib[0:], dibHeaderSize) // biSize
+	le.PutUint32(dib[4:], uint32(w))     // biWidth
+	le.PutUint32(dib[8:], uint32(h))     // biHeight (positive = bottom-up)
+	le.PutUint16(dib[12:], 1)            // biPlanes
+	le.PutUint16(dib[14:], 32)           // biBitCount
+	le.PutUint32(dib[16:], biRGB)        // biCompression
+	// biSizeImage (20) left 0 for BI_RGB; metrics/clrUsed/clrImportant left 0.
+
+	px := dib[dibHeaderSize:]
+	for y := 0; y < h; y++ {
+		srcY := h - 1 - y // bottom-up
+		row := px[y*w*4 : (y+1)*w*4]
+		for x := 0; x < w; x++ {
+			r, g, b_, a := img.At(b.Min.X+x, b.Min.Y+srcY).RGBA()
+			row[x*4+0] = uint8(b_ >> 8) // B
+			row[x*4+1] = uint8(g >> 8)  // G
+			row[x*4+2] = uint8(r >> 8)  // R
+			row[x*4+3] = uint8(a >> 8)  // A
+		}
+	}
+	return dib, nil
+}
+
+// dibToPNG converts a BI_RGB DIB (32bpp or 24bpp) to a PNG image.
+func dibToPNG(dib []byte) ([]byte, error) {
+	if len(dib) < dibHeaderSize {
+		return nil, ErrNoImage
+	}
+	le := binary.LittleEndian
+	w := int(int32(le.Uint32(dib[4:])))
+	h := int32(le.Uint32(dib[8:]))
+	bitCount := le.Uint16(dib[14:])
+	compression := le.Uint32(dib[16:])
+
+	if w <= 0 || h == 0 {
+		return nil, ErrNoImage
+	}
+	if compression != biRGB {
+		return nil, fmt.Errorf("clipboard: unsupported DIB compression %d", compression)
+	}
+
+	height := int(h)
+	if h < 0 {
+		height = -height
+	}
+	bottomUp := h > 0
+
+	img := image.NewRGBA(image.Rect(0, 0, w, height))
+	src := dib[dibHeaderSize:]
+
+	switch bitCount {
+	case 32:
+		stride := w * 4
+		for y := 0; y < height; y++ {
+			srcY := y
+			if bottomUp {
+				srcY = height - 1 - y
+			}
+			row := src[srcY*stride : (srcY+1)*stride]
+			for x := 0; x < w; x++ {
+				img.SetRGBA(x, y, color.RGBA{row[x*4+2], row[x*4+1], row[x*4+0], row[x*4+3]})
+			}
+		}
+	case 24:
+		stride := (w*3 + 3) &^ 3 // rows padded to 4-byte boundary
+		for y := 0; y < height; y++ {
+			srcY := y
+			if bottomUp {
+				srcY = height - 1 - y
+			}
+			row := src[srcY*stride : srcY*stride+w*3]
+			for x := 0; x < w; x++ {
+				img.SetRGBA(x, y, color.RGBA{row[x*3+2], row[x*3+1], row[x*3+0], 255})
+			}
+		}
+	default:
+		return nil, fmt.Errorf("clipboard: unsupported DIB bit count %d", bitCount)
+	}
+
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, img); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}