helper_functions.c

#include "image.h"

void error(int e) {
	switch (e) {
	case 1:
		fprintf(stderr, "Error opening files!\n");
		break;
	case 2:
		fprintf(stderr, "Error in allocation!\n");
		break;
	case 3:
		fprintf(stderr, "Images must have the same dimensions to perform this operation!\n");
		break;
	}
	exit(e);
}

Image* loadImage(char name[]) {
	FILE *in = fopen(name, "rb");
	if (!in) error(1);

	Image *i = malloc(sizeof(Image));
	if (!i) error(2);
	fread(i->header, sizeof(unsigned char), HEADER_LENGTH, in);
	i->width = *(int*)&i->header[18];
	i->height = *(int*)&i->header[22];
	i->bitDepth = *(int*)&i->header[28];
	i->offset = *(int*)&i->header[10];

	i->size = i->width * i->height;

	if (i->bitDepth <= 8)
		fread(i->colorTable, sizeof(unsigned char), COLOR_TABLE_LENGTH, in);
	else i->size *= i->bitDepth / 8;	// color

	i->gap1Length = 0;
	i->gap1 = NULL;
	int c;
	while (ftell(in) < i->offset) {
		c = getc(in);
		i->gap1 = realloc(i->gap1, (i->gap1Length + 1) * sizeof(unsigned char));
		if (!i->gap1) error(2);
		i->gap1[i->gap1Length++] = c;
	}

	i->data = malloc(i->size * sizeof(unsigned char));
	if (!i->data) error(2);

	fread(i->data, sizeof(unsigned char), i->size, in);

	/*
		Razliciti alati za konverziju u .bmp format dodaju razlicite footere na kraj fajla koji nam nisu bitni za obradu,
		ali moraju postojati i u izlaznom fajlu da bi format bio ispravan. Kako je duzina footera nepoznata, citamo znak
		po znak do kraja fajla i vrsimo potrebnu realokaciju dinamicke memorije.
	*/
	i->gap2Length = 0;
	i->gap2 = NULL;
	while ((c = getc(in)) != EOF) {
		i->gap2 = realloc(i->gap2, (i->gap2Length + 1) * sizeof(unsigned char));
		if (!i->gap2) error(2);
		i->gap2[i->gap2Length++] = c;
	}

	fclose(in);
	return i;
}

void exportImage(Image *i, char name[]) {
	FILE *out = fopen(name, "wb");
	if (!out) error(1);
	fwrite(i->header, sizeof(unsigned char), HEADER_LENGTH, out);
	if (i->bitDepth <= 8)
		fwrite(i->colorTable, sizeof(unsigned char), COLOR_TABLE_LENGTH, out);
	if (i->gap1Length)
		fwrite(i->gap1, sizeof(unsigned char), i->gap1Length, out);
	fwrite(i->data, sizeof(unsigned char), i->size, out);
	if (i->gap2Length)
		fwrite(i->gap2, sizeof(unsigned char), i->gap2Length, out);
	fclose(out);
}