Program Will not run.

[namegame]

I have written a program to convert an image from color to Sepia color tone. However, when I try to run it using
./a.out input.ppm output.ppm , it will not run.



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

int main(int argc, char *argv[]){

int x;
int y;
int width;
int height;
int index;
pixel_t *pixel;

unsigned char *inputImage;
unsigned char *outputImage;

inputImage = (unsigned char *)malloc (sizeof(pixel_t) * width * height);
outputImage = (unsigned char *)malloc (sizeof(pixel_t) * width * height);


FILE *input;
FILE *output;


if (argc < 3){
fprintf(stderr,"Incorrect input.\n");
fprintf(stderr,"Exiting.");
exit(1);
}

input = fopen(argv[1], "r");
output = fopen(argv[2], "w");

if ( input == NULL || output == NULL){
fprintf(stderr,"Error opening file.\n");
fprintf(stderr,"Exiting.");
exit(2);
}


readHeader (&width, &height, input);

pixel = (pixel_t *) malloc(sizeof(pixel_t));

input = malloc (sizeof(pixel_t) * width * height);
output = malloc(sizeof(pixel_t) * width * height);


fread(inputImage, sizeof(pixel_t), width * height, input);
for(y = 0; y < height; y++){

for(x = 0; x < width; x++){

index = sizeof(pixel_t) * y * width + sizeof(pixel_t) * x;
pixel->r = inputImage[index];
pixel->g = inputImage[index + 1];
pixel->b = inputImage[index + 2];

grayPixel(pixel);
sepiaPixel(pixel);

outputImage[index] = pixel->r;
outputImage[index + 1] = pixel->g;
outputImage[index + 2] = pixel->b;
}
}

makeHeader( width, height, input);
fwrite(outputImage, sizeof(pixel_t), width * height, output);

free(inputImage);
free(outputImage);
fclose(input);
fclose(output);

return 0;
}


void grayPixel(pixel_t *pixel){
int sum;
pixel->r = pixel->r * 0.3;
pixel->g = pixel->g * 0.5;
pixel->b = pixel->b * 0.2;
sum = pixel->r + pixel->g + pixel->b;
pixel->r = sum;
pixel->g = sum;
pixel->b = sum;
}


void sepiaPixel(pixel_t *pixel){
if (pixel->r < 60){
pixel->r = pixel->r * 0.9;
pixel->g = pixel->g * 0.9;
pixel->b = pixel->b * 0.9;
}
else if (pixel->r >= 60 && pixel->r < 190){
pixel->b = pixel->b * 0.8;
}
else {
pixel->b = pixel->b * 0.9;
}

}



Any suggestions/ideas will be welcome.

[Can+~]

Difficult to tell where the error is.

On a side note, if you really really need to use sepia tones, there's a utility on bash called "imagemagick", which can produce sepia tones (http://www.imagemagick.org/script/command-line-options.php#sepia-tone):


convert -sepia-tone 80% input_image.png output_image.png

[namegame]

I appreciate the info, however, this is an assignment due in my computer science class. I know this forum is touchy on people asking about homework, however, I feel as if I am well within the rules.

[Can+~]

I appreciate the info, however, this is an assignment due in my computer science class. I know this forum is touchy on people asking about homework, however, I feel as if I am well within the rules.

When you do:


outputImage[index + 2]

I noticed that input/outputImage are made out of pixel_t, that would mean, that each [x] you advance, you're actually advancing 1 pixel. So if you do [index + x] you're advancing x amount of pixels, instead of accessing the RGB values they contain.

I think it would be:


pixel->r = inputImage[index]->r;
pixel->g = inputImage[index]->g;
pixel->b = inputImage[index]->b;

If you access element [index+x] on the end of the image, it will point outside of the malloc space, causing segmentation fault.

[namegame]

that makes sense to me, however, in a previous program, the code was as I originally stated, and it worked flawlessly, the changes in this program were file I/O, command line arguments, and using typedef struct. I didn't really change much of the "meat" of the program.

[WW]

The variable input is of type FILE*, so this line


input = malloc (sizeof(pixel_t) * width * height);

does not make sense. You've changed input to point to a block of memory, but then you call fread with input as the last argument. You have a similar problem with the variable output.