C Programming Code Examples
C > Small Programs Code Examples
Get color and coordinates for each pixel
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/* Get color and coordinates for each pixel */
#include <stdio.h>
#include <gd.h>
int main(int argc, char *argv[]) {
FILE *fp = {0};
gdImagePtr img;
int x = 0;
int y = 0;
int width = 0;
int height = 0;
if(argc != 2) {
fprintf(stderr, "Usage: gixel image.png\n");
return 1;
}
fp = fopen(argv[1], "rb");
if(fp == NULL) {
fprintf(stderr, "Error - fopen(%s)\n", argv[1]);
return 1;
}
img = gdImageCreateFromPng(fp);
fclose(fp);
width = gdImageSX(img);
height = gdImageSY(img);
for(x = 0; x < width; x++)
for(y = 0; y < height; y++)
printf("%d,%d:%X\n", x, y, gdImageGetPixel(img, x, y));
gdImageDestroy(img);
return 0;
}
The open() function shall establish the connection between a file and a file descriptor. It shall create an open file description that refers to a file and a file descriptor that refers to that open file description. The file descriptor is used by other I/O functions to refer to that file. The path argument points to a pathname naming the file. The open() function shall return a file descriptor for the named file that is the lowest file descriptor not currently open for that process. The open file description is new, and therefore the file descriptor shall not share it with any other process in the system. The FD_CLOEXEC file descriptor flag associated with the new file descriptor shall be cleared.
Open file. Opens the file whose name is specified in the parameter filename and associates it with a stream that can be identified in future operations by the FILE pointer returned. The operations that are allowed on the stream and how these are performed are defined by the mode parameter. The returned stream is fully buffered by default if it is known to not refer to an interactive device (see setbuf). The returned pointer can be disassociated from the file by calling fclose or freopen. All opened files are automatically closed on normal program termination.
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