ascii_lend.c

#include <stdio.h>
#include <stdlib.h>

enum {
    MAX_BRIGHT = 36 
};
char ASCII[MAX_BRIGHT] = {
    ' ', '.', '\'', '`', '\'', '-', '^', '\"', '!',
    '>', ';', '=', '0', 'i', 'j', 'l', 't', 'c', 'f',
    'o', 'a', 'V', '5', 'e', 'b', 'D', 'p', 'g', 'B',
    'm', 'H', 'H', 'H', 'M', 'M', '@'
};

typedef unsigned char byte; 
typedef byte pixel;         
void image_to_ascii(pixel image[], int height, int width, int ascii_width)
{
    int block_w = width/ascii_width;    /* egy karakter ennyi pixel széles lesz */
    int block_h = block_w * 2;          /* és ennyi magas */

    int h, w;
    for (h = 0; h < height/block_h; ++h) {  /* minden ascii sorra és oszlopra */
        for (w = 0; w < ascii_width; ++w) {
            int i, j, b = 0;    /* b a fényesség */
            for (i = 0; i < block_h; ++i) { /* minden pixelre */
                for (j = 0; j < block_w; ++j) {
                    int pix_h = h*block_h+i;
                    int pix_w = w*block_w+j;
                    b += image[pix_h*width + pix_w]; /* 2D indexelés */
                }
            }
            b *= MAX_BRIGHT / 256.0 / (block_w * block_h);
            printf("%c", ASCII[b]);     /* karakter kikeresése és kiírása */
        }
        printf("\n");
    }
}

int read_bigendian(FILE *fp, int b)
{
    int i;
    int ret = 0;
    byte bytes[16];
    fread(bytes, 1, b, fp);
    for (i = 0; i < b; ++i)
        ret = 256 * ret + bytes[i];
    return ret;
}

int read_littleendian(FILE *fp, int b)
{
    int i;
    int ret = 0;
    byte bytes[16];
    fread(bytes, 1, b, fp);
    for (i = b-1; i >= 0; --i)
        ret = 256 * ret + bytes[i];
    return ret;
}

pixel *read_image(char *fname, int *height, int *width)
{
    pixel *image = NULL;
    int h, w;   /* magasság, szélésség */
    FILE *fp = fopen(fname, "rb");
    if (fp == NULL) {
        fprintf(stderr, "Cannot open file %s for binary reading", fname);
        return NULL;
    }
    h = read_littleendian(fp, 2);
    w = read_littleendian(fp, 2);
    image = (pixel *)malloc(h * w * sizeof(pixel));
    if (image == NULL) {
        fprintf(stderr, "Cannot allocate memory for %d x %d pixels\n", h, w);
        fclose(fp);
        return NULL;
    }
    if (fread(image, sizeof(pixel), h * w, fp) != h * w) {
        fprintf(stderr, "Cannot read %d x %d pixels from file %s\n", h, w, fname);
        free(image);
        fclose(fp);
        return NULL;
    }

    fclose(fp);
    *height = h;
    *width = w;
    return image;
}

int main(void)
{
    int width, height, w_ascii;
    char fname[100];
    pixel *image;

    printf("Filename: ");       scanf("%s", fname);
    printf("ascii width: ");    scanf("%d", &w_ascii);

    image = read_image(fname, &height, &width);
    if (image == NULL)
        return 1;

    image_to_ascii(image, height, width, w_ascii);

    free(image);
    return 0;
}