Easily read and write bitmaps image files.

bmp.c

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

typedef struct header {
	unsigned char signature[2];
	unsigned int fileSize;
	unsigned int reserved;
	unsigned int dataOffset;
} Header;

typedef struct infoHeader {
	unsigned int size;
	unsigned int width;
	unsigned int height;
	unsigned short planes;
	unsigned short bitsPerPixel;
	unsigned int compression;
	unsigned int imageSize;
	unsigned int xPixelsPerM;
	unsigned int yPixelsPerM;
	unsigned int colorUsed;
	unsigned int importantColors;
	
} InfoHeader;

typedef struct colorTable {
	char r;
	char g;
	char b;
	char reserved;
	
} ColorTable;

typedef struct image {
	Header header;
	InfoHeader infoHeader;
	ColorTable colorTable;
	void *pixels;
	
} Image;

Image *LoadBMP(const char *file) {
	FILE *fp;
	Image *image;
	size_t size;
	
	if ((fp = fopen(file, "rb")) == NULL) return NULL;
	
	if ((image = malloc(sizeof(Image))) == NULL)
	{
		fclose(fp);
		return NULL;
	}
	
	fread(image->header.signature, 				sizeof(image->header.signature), 1, fp);
	fread(&image->header.fileSize, 				sizeof(image->header.fileSize), 1, fp);
	fread(&image->header.reserved, 				sizeof(image->header.reserved), 1, fp);
	fread(&image->header.dataOffset, 			sizeof(image->header.dataOffset), 1, fp);
	
	fread(&image->infoHeader.size, 				sizeof(image->infoHeader.size), 1, fp);
	fread(&image->infoHeader.width, 			sizeof(image->infoHeader.width), 1, fp);
	fread(&image->infoHeader.height, 			sizeof(image->infoHeader.height), 1, fp);
	fread(&image->infoHeader.planes, 			sizeof(image->infoHeader.planes), 1, fp);
	fread(&image->infoHeader.bitsPerPixel, 			sizeof(image->infoHeader.bitsPerPixel), 1, fp);
	fread(&image->infoHeader.compression, 			sizeof(image->infoHeader.compression), 1, fp);
	fread(&image->infoHeader.imageSize, 			sizeof(image->infoHeader.imageSize), 1, fp);
	fread(&image->infoHeader.xPixelsPerM, 			sizeof(image->infoHeader.xPixelsPerM), 1, fp);
	fread(&image->infoHeader.yPixelsPerM, 			sizeof(image->infoHeader.yPixelsPerM), 1, fp);
	fread(&image->infoHeader.colorUsed, 			sizeof(image->infoHeader.colorUsed), 1, fp);
	fread(&image->infoHeader.importantColors, 		sizeof(image->infoHeader.importantColors), 1, fp);
	
	fread(&image->colorTable.r, 				sizeof(image->colorTable.r), 1, fp);
	fread(&image->colorTable.g, 				sizeof(image->colorTable.g), 1, fp);
	fread(&image->colorTable.b, 				sizeof(image->colorTable.b), 1, fp);
	fread(&image->colorTable.reserved, 			sizeof(image->colorTable.reserved), 1, fp);
	size = image->infoHeader.width * image->infoHeader.height * image->infoHeader.planes * image->infoHeader.bitsPerPixel;
	image->pixels = malloc(size);
	fread(image->pixels, size, 1, fp);
	
	fclose(fp);
	return image;
}

bool WriteBMP(const char *file, Image image) {
	FILE *fp;
	size_t size;
	
	if ((fp = fopen(file, "wb")) == NULL) return false;
	
	fwrite(image.header.signature, 				sizeof(image.header.signature), 1, fp);
	fwrite(&image.header.fileSize, 				sizeof(image.header.fileSize), 1, fp);
	fwrite(&image.header.reserved, 				sizeof(image.header.reserved), 1, fp);
	fwrite(&image.header.dataOffset, 			sizeof(image.header.dataOffset), 1, fp);
	
	fwrite(&image.infoHeader.size, 				sizeof(image.infoHeader.size), 1, fp);
	fwrite(&image.infoHeader.width, 			sizeof(image.infoHeader.width), 1, fp);
	fwrite(&image.infoHeader.height, 			sizeof(image.infoHeader.height), 1, fp);
	fwrite(&image.infoHeader.planes, 			sizeof(image.infoHeader.planes), 1, fp);
	fwrite(&image.infoHeader.bitsPerPixel, 			sizeof(image.infoHeader.bitsPerPixel), 1, fp);
	fwrite(&image.infoHeader.compression, 			sizeof(image.infoHeader.compression), 1, fp);
	fwrite(&image.infoHeader.imageSize, 			sizeof(image.infoHeader.imageSize), 1, fp);
	fwrite(&image.infoHeader.xPixelsPerM, 			sizeof(image.infoHeader.xPixelsPerM), 1, fp);
	fwrite(&image.infoHeader.yPixelsPerM, 			sizeof(image.infoHeader.yPixelsPerM), 1, fp);
	fwrite(&image.infoHeader.colorUsed, 			sizeof(image.infoHeader.colorUsed), 1, fp);
	fwrite(&image.infoHeader.importantColors, 		sizeof(image.infoHeader.importantColors), 1, fp);
	
	fwrite(&image.colorTable.r, 				sizeof(image.colorTable.r), 1, fp);
	fwrite(&image.colorTable.g, 				sizeof(image.colorTable.g), 1, fp);
	fwrite(&image.colorTable.b, 				sizeof(image.colorTable.b), 1, fp);
	fwrite(&image.colorTable.reserved, 			sizeof(image.colorTable.reserved), 1, fp);
	
	size = image.infoHeader.width * image.infoHeader.height * image.infoHeader.planes * image.infoHeader.bitsPerPixel;
	fwrite(image.pixels, size, 1, fp);
	
	fclose(fp);
	
	return true;
}

void FreeBMP(Image *image) {
	free(image->pixels);
	free(image);
}

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

int main(void) {
	
	Image *image = LoadBMP("bitmap.bmp");
	
	printf("%i\n", image->infoHeader.compression);
	printf("%i\n", image->infoHeader.width);
	printf("%i\n", image->infoHeader.height);
	printf("%i\n", image->infoHeader.planes);
	printf("%i\n", image->infoHeader.bitsPerPixel);
	
	if (WriteBMP("bitmap_copy.bmp", *image))
	{
		printf("done!\n");
	}
	
	FreeBMP(image);
	
	return 0;
}