reading image

how can i read jpg format images (or) pixel values

First of all, let's assume that you're not using TurboC as your compiler.

That being the case, the easiest way to read a JPG file into a format where you can read pixels is to use a library.
libjpeg - Wikipedia

Yes, you can use fopen() to open the file, and fread() to read the whole file into memory.
But extracting pixels from the binary data involves a LOT of work, and a LOT of very serious maths.
If you want reasonable results in anything less than 6 months, then use a library.

Here's code for loading JPEGs and all the other popular file formats for good measure.

GitHub - MalcolmMcLean/babyxrc: Resource compiler, packages images, fonts, cursors, etc as compilable C source. Portable ANSI C.

stb_image makes reading images quite painless. It's just a single header file you include in your own code, and that's it. Also it's a public domain license.

Here's a dumb example of reading the first 10 pixels of a JPG file...

Code:

---

#include <stdio.h>

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

const size_t NUM_PIXELS_TO_PRINT = 10U;

int main(void) {
    int width, height, comp;
    unsigned char *data = stbi_load("image.jpg", &width, &height, &comp, 0);
    if (data) {
        printf("width = %d, height = %d, comp = %d (channels)\n", width, height, comp);
        for (size_t i = 0; i < NUM_PIXELS_TO_PRINT * comp; i++) {
            printf("%02x%s", data[i], ((i + 1) % comp) ? "" : "\n");
        }
        printf("\n");
    }
    return 0;
}

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