我正在尝试从客户端缓冲区创建服务器端RGBA像素图。 CreatePixmap＆amp; CreateImage适用于32位和24位，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
服务器支持32位像素映射（xdpyinfo输出：https://gist.github.com/2582961）。在ubuntu 12.04（X.Org版本：1.11.3）和OSX与X.app（X.Org版本：1.10.3）上的行为相同
为什么以下代码失败？
#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：看起来我终于得到了答案：使用与pixmap相关联的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);
}
}
答案 0 :(得分：5)
问题在于DefaultGC()，它返回具有系统默认屏幕位深度的GC。如果你看一下gist paste的第53行，你会看到这是24：
根窗口深度：24架
在第63行，您会看到它默认使用0x22，在第64行到第70行中有更详细的显示：
visual:
visual id: 0x22
class: TrueColor
depth: 24 planes
available colormap entries: 256 per subfield
red, green, blue masks: 0xff0000, 0xff00, 0xff
significant bits in color specification: 8 bits
你可能会做得更好一点，但作为一个开始，你可以试试这个：
注意：这使用系统视觉效果，因此最有可能只支持24或32的深度。
#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#ifdef DEBUG
int dbg = 1;
#else
int dbg = 0;
#endif
/* Return a GC based on depth */
int gc_depth(int depth, Display *dpy, Window scr, Window root, GC *gc)
{
Window win;
Visual *visual;
XVisualInfo vis_info;
XSetWindowAttributes win_attr;
unsigned long win_mask;
if(!XMatchVisualInfo(dpy, scr, depth, TrueColor, &vis_info)) {
fprintf(stderr,
" * ERR: %d depth not supported\n",
depth
);
return 1;
}
visual = vis_info.visual;
win_attr.colormap = XCreateColormap(dpy, root, visual, AllocNone);
win_attr.background_pixel = 0;
win_attr.border_pixel = 0;
win_mask = CWBackPixel | CWColormap | CWBorderPixel;
win = XCreateWindow(
dpy, root,
0, 0,
100, 100, /* dummy size */
0, depth,
InputOutput, visual,
win_mask, &win_attr);
/* To flush out any errors */
if (dbg) XSync(dpy, True);
*gc = XCreateGC(dpy, win, 0, 0);
if (dbg) XSync(dpy, True);
XDestroyWindow(dpy, win);
if (dbg) XSync(dpy, True);
return 0;
}
int main(void)
{
int w = 100;
int h = 100;
int depth = 32;
int bitmap_pad = 32;
int bpl = 0;
Display *dpy;
Window root;
Window scr;
GC gc;
int root_depth;
Pixmap pm;
XImage *img;
unsigned char *buf_img;
if(!(dpy = XOpenDisplay(NULL))) {
fprintf(stderr,
" * ERR: Failed to open display.\n");
return 1;
}
#ifdef DEBUG
/* To get errors in order, slows down
* One can also define int _Xdebug = 1;
* */
XSynchronize(dpy, True);
#endif
root = XDefaultRootWindow(dpy);
scr = XDefaultScreen(dpy);
if ((buf_img = malloc(w * h * 4)) == NULL) {
fprintf(stderr,
" * ERR: Unable to alloacte %d bytes\n",
w * h * 4);
return 1;
}
root_depth = DefaultDepth(dpy, scr);
fprintf(stderr,
"Default depth: %d\n",
root_depth);
/* This should be doen more nice */
if (depth != root_depth) {
if (gc_depth(depth, dpy, scr, root, &gc) != 0)
return 1;
} else {
gc = DefaultGC(dpy, 0);
}
img = XCreateImage(
dpy, CopyFromParent,
depth, ZPixmap,
0, (char *)buf_img,
w, h,
bitmap_pad, bpl);
/* To flush out any errors */
if (dbg) XSync(dpy, True);
pm = XCreatePixmap(
dpy, root,
w, h,
depth);
if (dbg) XSync(dpy, True);
XPutImage(
dpy, pm,
gc, img,
0, 0,
0, 0,
w, h);
if (dbg) XSync(dpy, True);
XFreePixmap(dpy, pm);
XDestroyImage(img);
XFreeGC(dpy, gc);
if (dbg) XSync(dpy, True);
fprintf(stderr,
"OK!\n");
return 0;
}
答案 1 :(得分：2)
好吧，如果你只是创建一个通过一个32位参数的绘图的GC，你的代码适用于32位图像。 XCreateGC（dpy，drawable，0,0），其中drawable可以是32位深度的像素图。它对我来说很完美。