使用 xlib 绘制具有透明颜色的图形

Question

使用 Xlib：我正在尝试显示具有透明颜色（颜色）的像素图。那是一种显示背景的颜色。目前使用 XCopyArea () 绘制完全不透明的像素图。我怎样才能使它透明（像 XDrawString 一样工作）？

谢谢

    GC pixgc = XCreateGC (XDisplay, pix, 0, NULL);
    XSetForeground (XDisplay, pixgc, ColourToXColour (RGB (0xff, 0xFF, 0xff)));
    XFillRectangle (XDisplay, pix, pixgc, 0, 0, 32, 32);
    XSetForeground (XDisplay, pixgc, ColourToXColour (RGB (0x00, 0x80, 0x80)));
    XDrawLine (XDisplay, pix, pixgc, 8, 8, 8 + 16, 8 + 16);
    XDrawLine (XDisplay, pix, pixgc, 8, 8 + 16, 8 + 16, 8);
    XDrawArc (XDisplay, pix, pixgc, 6, 6, 20, 20, 0, 270 * 64);
    XCopyArea (XDisplay, pix, Res->XWindow, DefaultGC (XDisplay, XScreen), 0, 0, 32, 32,  10, 50);

Answer 1

这是一种可能的解决方案。如果可能的话，我会重视更好的答案。

// Mask is Black & White. Areas in Source corresponding White areas in Mask are drawn on Dest
bool CopyArea (Drawable Source, Drawable Dest, Drawable Mask, GC gc, int x, int y, int Width, int Height, int DestX, int DestY)
  {
    int a, b;
    XGCValues gcv;
    int func;
    Pixmap Mask_;
    //
    // Clear effected pixels in Dest
    XGetGCValues (XDisplay, gc, GCFunction, &gcv);
    func = gcv.function;
    gcv.function = GXandInverted;
    XChangeGC (XDisplay, gc, GCFunction, &gcv);
    XCopyArea (XDisplay, Mask, Dest, gc, x, y, Width, Height, DestX, DestY);
    // Generate coloured Mask to OR into Dest
    Mask_ = XCreatePixmap (XDisplay, Dest, Width, Height, 24);   // First make a copy of Mask
    gcv.function = GXcopy;
    XChangeGC (XDisplay, gc, GCFunction, &gcv);
    XCopyArea (XDisplay, Mask, Mask_, gc, x, y, Width, Height, 0, 0);
    gcv.function = GXand;   // Then colour it to match pixels in Source
    XChangeGC (XDisplay, gc, GCFunction, &gcv);
    XCopyArea (XDisplay, Source, Mask_, gc, x, y, Width, Height, 0, 0);
    // Copy new coloured Mask into Dest
    gcv.function = GXor;
    XChangeGC (XDisplay, gc, GCFunction, &gcv);
    XCopyArea (XDisplay, Mask_, Dest, gc, 0, 0, Width, Height, DestX, DestY);
    // Restore gc & free new Mask
    gcv.function = func;
    XChangeGC (XDisplay, gc, GCFunction, &gcv);
    XFreePixmap (XDisplay, Mask_);
  }