Displaying two translucent images on each other with XRender - c

Question

So I was trying to display one translucent farbfeld image on top of another, often opaque farbfeld image (named f2.ff and f.ff in order) with the use of XRender to get the alpha compositing but due to the lack of examples on XRender and me being new to Xlib it does not work :)
and the translucent image which should have been displayed on top(f2.ff) is flickering weirdly.
Here is the code :
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#define STB_IMAGE_RESIZE_IMPLEMENTATION
#include "stb_image_resize.h"
#include <string.h>
#include <X11/Xlib.h>
#include <X11/extensions/Xrender.h>
typedef struct XWindow XWindow;
struct XWindow
{
Display * dpy;
Window root;
Visual * vis;
Colormap cmap;
XWindowAttributes attr;
XSetWindowAttributes swa;
Window win;
int screen;
unsigned int width;
unsigned int height;
Atom wm_delete_window;
};
struct head
{
char ma [7];
unsigned int w;
unsigned int h;
};
unsigned char * ffread(const char * path,unsigned int * w,unsigned int * h)
{
struct head * hh;
size_t filelen;
unsigned char * buffer;
unsigned short temp=0;
size_t i=0;
FILE * file;
file=fopen(path,"rb");
if(file == NULL)
{
puts("cant open the file");
exit(1);
}
hh=malloc(16*sizeof(unsigned short));
fread(hh,2,15,file);
if(strcmp("farbfeld",hh->ma))
{
puts("Invalid file format");
exit(1);
}
*w=ntohl(hh->w);
*h=ntohl(hh->h);
printf("%d %d\n",*w,*h);
filelen=(*w)*(*h)*4;
buffer=malloc(filelen*sizeof(char));
fseek(file,16,SEEK_SET);
for(; i<filelen; i++)
{
fread(&temp,2,1,file);
if(i%4==0||i==0)
{
buffer[i+2]=(ntohs(temp)/257);
}
else if(i%2==0)
{
buffer[i-2]=(ntohs(temp)/257);
}
else
{
buffer[i]=(ntohs(temp)/257);
}
}
fclose(file);
return buffer;
}
int main(void)
{
XWindow xw;
unsigned char * data;
unsigned char * bdata;
unsigned char * im2;
unsigned int wim=0,him=0, w=0,h=0, wim2=0,him2 =0;
XImage * image;
Pixmap pix;
Picture pic;
Picture picdst;
GC gc;
XImage * imagebg;
Pixmap pix2;
Picture pic2bg;
memset(&xw, 0, sizeof xw);
xw.dpy = XOpenDisplay(NULL);
if(!xw.dpy) puts("Could not open a display; perhaps $DISPLAY is not set?");
xw.root = DefaultRootWindow(xw.dpy);
xw.screen = XDefaultScreen(xw.dpy);
xw.vis = XDefaultVisual(xw.dpy, xw.screen);
xw.cmap = XCreateColormap(xw.dpy,xw.root,xw.vis,AllocNone);
xw.swa.colormap = xw.cmap;
xw.swa.event_mask =
ExposureMask | KeyPressMask | KeyReleaseMask |
ButtonPress | ButtonReleaseMask| ButtonMotionMask |
Button1MotionMask | Button3MotionMask | Button4MotionMask | Button5MotionMask|
PointerMotionMask | KeymapStateMask;
h=DisplayHeight(xw.dpy,xw.screen);
w=DisplayWidth(xw.dpy,xw.screen);
xw.win = XCreateWindow(xw.dpy, xw.root, 0, 0, w, h, 0,
XDefaultDepth(xw.dpy, xw.screen), InputOutput,
xw.vis, CWEventMask | CWColormap, &xw.swa);
XStoreName(xw.dpy, xw.win, "X11");
XMapWindow(xw.dpy, xw.win);
xw.wm_delete_window = XInternAtom(xw.dpy, "WM_DELETE_WINDOW", False);
XSetWMProtocols(xw.dpy, xw.win, &xw.wm_delete_window, 1);
XGetWindowAttributes(xw.dpy, xw.win, &xw.attr);
xw.width = (unsigned int)xw.attr.width;
xw.height = (unsigned int)xw.attr.height;
data=ffread("./f.ff",&wim,&him);
bdata=(unsigned char *)malloc(w*h*4);
stbir_resize_uint8(data,wim,him,0,bdata,w,h,0,4);
im2=ffread("./f2.ff",&wim2,&him2);
picdst=XRenderCreatePicture(xw.dpy,xw.win,XRenderFindStandardFormat(xw.dpy, PictStandardRGB24),0,0);
image=XCreateImage(xw.dpy,CopyFromParent,32,ZPixmap, 0,(char *)im2,wim2, him2,4*8, 4 * wim2);
pix=XCreatePixmap(xw.dpy,xw.win,wim2,him2,32);
gc=XCreateGC(xw.dpy,pix,0,NULL);
XPutImage(xw.dpy,pix,gc,image,0,0,0,0,wim2,him2);
pic=XRenderCreatePicture(xw.dpy,pix,XRenderFindStandardFormat(xw.dpy, PictStandardARGB32),0,0);
imagebg =XCreateImage(xw.dpy,CopyFromParent,32,ZPixmap, 0,(char *)bdata,w, h,4*8, 4 * w);
pix2=XCreatePixmap(xw.dpy,xw.win,w,h,32);
gc=XCreateGC(xw.dpy,pix2,0,NULL);
XPutImage(xw.dpy,pix2,gc,imagebg,0,0,0,0,w,h);
pic2bg=XRenderCreatePicture(xw.dpy,pix2,XRenderFindStandardFormat(xw.dpy, PictStandardARGB32),0,0);
while(1)
{
pic2bg=XRenderCreatePicture(xw.dpy,pix2,XRenderFindStandardFormat(xw.dpy, PictStandardARGB32),0,0);
picdst=XRenderCreatePicture(xw.dpy,xw.win,XRenderFindStandardFormat(xw.dpy, PictStandardRGB24),0,0);
pic=XRenderCreatePicture(xw.dpy,pix,XRenderFindStandardFormat(xw.dpy, PictStandardARGB32),0,0);
XRenderComposite(xw.dpy,PictOpSrc,pic,None,picdst,0,0,0,0,0,0,wim2,him2);
XRenderComposite(xw.dpy,PictOpSrc,pic2bg,None,picdst,0,0,0,0,0,0,w,h);
XRenderFreePicture(xw.dpy,picdst);
XRenderFreePicture(xw.dpy,pic2bg);
XRenderFreePicture(xw.dpy,pic);
}
}