【发布时间】：2012-05-16 13:30:10
【问题描述】：
我正在尝试从客户端缓冲区创建服务器端 RGBA 像素图。 CreatePixmap 和 CreateImage 在 32 位和 24 位下工作正常，但 XPutImage 导致服务器返回匹配错误
X Error of failed request: BadMatch (invalid parameter attributes)
Major opcode of failed request: 72 (X_PutImage)
Serial number of failed request: 8
Current serial number in output stream: 8
服务器确实支持 32 位像素图（xdpyinfo 输出：https://gist.github.com/2582961）。在 ubuntu 12.04（X.Org 版本：1.11.3）和带有 X.app（X.Org 版本：1.10.3）的 OSX 上的行为相同
为什么下面的代码会失败？
#include <stdlib.h>
#include <X11/Xlib.h>
int main(int argc, char **argv)
{
int width = 100;
int height = 100;
int depth = 32; // works fine with depth = 24
int bitmap_pad = 32; // 32 for 24 and 32 bpp, 16, for 15&16
int bytes_per_line = 0; // number of bytes in the client image between the start of one scanline and the start of the next
Display *display=XOpenDisplay(0);
unsigned char *image32=(unsigned char *)malloc(width*height*4);
XImage *img = XCreateImage(display, CopyFromParent, depth, ZPixmap, 0, image32, width, height, bitmap_pad, bytes_per_line);
Pixmap p = XCreatePixmap(display, XDefaultRootWindow(display), width, height, depth);
XPutImage(display, p, DefaultGC(display, 0), img, 0, 0, 0, 0, width, height); // 0, 0, 0, 0 are src x,y and dst x,y
XEvent ev;
while (1) {
XNextEvent(display, &ev);
}
}
更新：看来我终于得到了答案：使用与 pixmap 关联的 GC 而不是 DefaultGC（具有根窗口深度）
#include <stdlib.h>
#include <X11/Xlib.h>
int main(int argc, char **argv)
{
int width = 100;
int height = 100;
int depth = 32; // works fine with depth = 24
int bitmap_pad = 32; // 32 for 24 and 32 bpp, 16, for 15&16
int bytes_per_line = 0; // number of bytes in the client image between the start of one scanline and the start of the next
Display *display=XOpenDisplay(0);
unsigned char *image32=(unsigned char *)malloc(width*height*4);
XImage *img = XCreateImage(display, CopyFromParent, depth, ZPixmap, 0, image32, width, height, bitmap_pad, bytes_per_line);
Pixmap p = XCreatePixmap(display, XDefaultRootWindow(display), width, height, depth);
XGCValues gcvalues;
GC gc = XCreateGC(display, p, 0, &gcvalues);
XPutImage(display, p, gc, img, 0, 0, 0, 0, width, height); // 0, 0, 0, 0 are src x,y and dst x,y
XEvent ev;
while (1) {
XNextEvent(display, &ev);
}
}
【问题讨论】：