What is the simplest RGB image format?

Question

I am working in C on a physics experiment, Young\'s interference experiment and i made a program who prints to file a huge bunch of pixels :

for         


        

Answer 1

Here's a minimal example that writes your image file with a minimal PPM header:

#include 
#include 

#include  // compile with gcc -lm

int main(){
    /* Setup for Young's interference image */
    #define width 256
    unsigned char raster_matrix[width*width], h[3];
    #define WAVE(x,y) sin(sqrt( (x)*(x)+(y)*(y) ) / 3.0)
    #define hue(c) (h[0] = c, h[1] = 128, h[2] = 255-c, h)

    int x, y, i = 0;
    for (y = 0; y < width; y++) for (x = 0; x < width; x++)
        raster_matrix[i++] = 128 + 64*(WAVE(x,y) + WAVE(x,width-y));


    /* Open PPM File */
    FILE *file = fopen("young.ppm", "wb"); if (!file) return -1;

    /* Write PPM Header */
    fprintf(file, "P6 %d %d %d\n", width, width, 255); /* width, height, maxval */

    /* Write Image Data */
    for (i=0; i < width*width; i++)
        fwrite(hue(raster_matrix[i]), 1, 3, file);

    /* Close PPM File */
    fclose(file);

    /* All done */
    return 0;
}

I wrote the header code based on the specs at http://netpbm.sourceforge.net/doc/ppm.html. For this image, the header is just a string of fifteen bytes: "P6 256 256 255\n".

The setup code here is slightly hackish, but makes it possible to concisely demonstrate the code with the exact for loop body given in the question.