init: 自 zomaintain/backend/rdplib 平移独立成库; module path 从上游 github.com/nakagami/grdp 改为 git.zeroonesoft.cn/golib/rdplib

2026-09-19 18:55:43 +08:00
commit 1096fbce9d
94 changed files with 36790 additions and 0 deletions
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+// image_dib.go 将 Windows 剪贴板的 CF_DIB（BITMAPINFO + 像素）转换为 PNG。
+//
+// 剪贴板截图类内容常见两种来源：现代应用直接提供 "PNG" 注册格式；老应用
+// （如 Server 上的画图）只提供 CF_DIB。本转换器覆盖最常见子集：
+// BI_RGB / BI_BITFIELDS 压缩、24/32bpp、底行优先（默认）与 top-down。
+package cliprdr
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"image"
+	"image/png"
+)
+
+// DIBToPNG 把 CF_DIB 数据解码并编码为 PNG；不支持的子集返回错误。
+func DIBToPNG(dib []byte) ([]byte, error) {
+	if len(dib) < 40 {
+		return nil, fmt.Errorf("dib too short: %d", len(dib))
+	}
+	biSize := binary.LittleEndian.Uint32(dib[0:4])
+	w := int(int32(binary.LittleEndian.Uint32(dib[4:8])))
+	hRaw := int32(binary.LittleEndian.Uint32(dib[8:12]))
+	topDown := hRaw < 0
+	h := int(hRaw)
+	if h < 0 {
+		h = -h
+	}
+	bpp := binary.LittleEndian.Uint16(dib[14:16])
+	compression := binary.LittleEndian.Uint32(dib[16:20])
+	if w <= 0 || h <= 0 || w > 16384 || h > 16384 {
+		return nil, fmt.Errorf("bad dimensions %dx%d", w, h)
+	}
+
+	var rMask, gMask, bMask uint32
+	pixOff := int(biSize)
+	switch compression {
+	case 0: // BI_RGB
+		rMask, gMask, bMask = 0x00FF0000, 0x0000FF00, 0x000000FF
+	case 3: // BI_BITFIELDS
+		if biSize >= 108 { // BITMAPV4HEADER/V5HEADER 内含掩码
+			rMask = binary.LittleEndian.Uint32(dib[40:44])
+			gMask = binary.LittleEndian.Uint32(dib[44:48])
+			bMask = binary.LittleEndian.Uint32(dib[48:52])
+		} else { // 三个 DWORD 掩码紧跟标准头
+			if pixOff+12 > len(dib) {
+				return nil, fmt.Errorf("missing bitfields masks")
+			}
+			rMask = binary.LittleEndian.Uint32(dib[pixOff:])
+			gMask = binary.LittleEndian.Uint32(dib[pixOff+4:])
+			bMask = binary.LittleEndian.Uint32(dib[pixOff+8:])
+			pixOff += 12
+		}
+	default:
+		return nil, fmt.Errorf("unsupported compression %d", compression)
+	}
+	if bpp != 24 && bpp != 32 {
+		return nil, fmt.Errorf("unsupported bpp %d", bpp)
+	}
+
+	stride := (w*int(bpp) + 31) / 32 * 4
+	if pixOff+stride*h > len(dib) {
+		return nil, fmt.Errorf("dib truncated: need %d, have %d", pixOff+stride*h, len(dib))
+	}
+
+	img := image.NewRGBA(image.Rect(0, 0, w, h))
+	for y := 0; y < h; y++ {
+		srcY := y
+		if !topDown {
+			srcY = h - 1 - y
+		}
+		row := dib[pixOff+srcY*stride:]
+		for x := 0; x < w; x++ {
+			var r8, g8, b8 uint8
+			if bpp == 32 {
+				v := binary.LittleEndian.Uint32(row[x*4:])
+				r8, g8, b8 = maskTo8(v, rMask), maskTo8(v, gMask), maskTo8(v, bMask)
+			} else {
+				o := x * 3
+				b8, g8, r8 = row[o], row[o+1], row[o+2]
+			}
+			i := img.PixOffset(x, y)
+			img.Pix[i], img.Pix[i+1], img.Pix[i+2], img.Pix[i+3] = r8, g8, b8, 255
+		}
+	}
+
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, img); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// maskTo8 把 mask 提取出的位域缩放为 8 位
+func maskTo8(v, mask uint32) uint8 {
+	if mask == 0 {
+		return 0
+	}
+	shift := 0
+	for mask&1 == 0 {
+		mask >>= 1
+		shift++
+	}
+	bits := 0
+	for mask != 0 {
+		mask >>= 1
+		bits++
+	}
+	val := (v >> uint(shift)) & ((1 << uint(bits)) - 1)
+	if bits < 8 {
+		return uint8(val<<(8-bits) | val>>(2*uint(bits)-8))
+	}
+	return uint8(val >> uint(bits-8))
+}