libbmp.c

/* Copyright 2016 - 2017 Marc Volker Dickmann
 * Project: LibBMP
 */
#include <stdio.h>
#include <stdlib.h>
#include "libbmp.h"

// BMP_HEADER

void
bmp_header_init_df (bmp_header *header,
                    const int   width,
                    const int   height)
{
	header->bfSize = (sizeof (bmp_pixel) * width + BMP_GET_PADDING (width))
	                  * abs (height);
	header->bfReserved = 0;
	header->bfOffBits = 54;
	header->biSize = 40;
	header->biWidth = width;
	header->biHeight = height;
	header->biPlanes = 1;
	header->biBitCount = 24;
	header->biCompression = 0;
	header->biSizeImage = 0;
	header->biXPelsPerMeter = 0;
	header->biYPelsPerMeter = 0;
	header->biClrUsed = 0;
	header->biClrImportant = 0;
}

enum bmp_error
bmp_header_write (const bmp_header *header,
                  FILE             *img_file)
{
	if (header == NULL)
	{
		return BMP_HEADER_NOT_INITIALIZED; 
	}
	else if (img_file == NULL)
	{
		return BMP_FILE_NOT_OPENED;
	}
	
	// Since an adress must be passed to fwrite, create a variable!
	const unsigned short magic = BMP_MAGIC;
	fwrite (&magic, sizeof (magic), 1, img_file);
	
	// Use the type instead of the variable because its a pointer!
	fwrite (header, sizeof (bmp_header), 1, img_file);
	return BMP_OK;
}

enum bmp_error
bmp_header_read (bmp_header *header,
                 FILE       *img_file)
{
	if (img_file == NULL)
	{
		return BMP_FILE_NOT_OPENED;
	}
	
	// Since an adress must be passed to fread, create a variable!
	unsigned short magic;
	
	// Check if its an bmp file by comparing the magic nbr:
	if (fread (&magic, sizeof (magic), 1, img_file) != 1 ||
	    magic != BMP_MAGIC)
	{
		return BMP_INVALID_FILE;
	}
	
	if (fread (header, sizeof (bmp_header), 1, img_file) != 1)
	{
		return BMP_ERROR;
	}

	return BMP_OK;
}

// BMP_PIXEL

void
bmp_pixel_init (bmp_pixel           *pxl,
                const unsigned char  red,
                const unsigned char  green,
                const unsigned char  blue)
{
	pxl->red = red;
	pxl->green = green;
	pxl->blue = blue;
}

// BMP_IMG

void
bmp_img_alloc (bmp_img *img)
{
	const size_t h = abs (img->img_header.biHeight);
	
	// Allocate the required memory for the pixels:
	img->img_pixels = malloc (sizeof (bmp_pixel*) * h);
	
	for (size_t y = 0; y < h; y++)
	{
		img->img_pixels[y] = malloc (sizeof (bmp_pixel) * img->img_header.biWidth);
	}
}

void
bmp_img_init_df (bmp_img   *img,
                 const int  width,
                 const int  height)
{
	// INIT the header with default values:
	bmp_header_init_df (&img->img_header, width, height);
	bmp_img_alloc (img);
}

void
bmp_img_free (bmp_img *img)
{
	const size_t h = abs (img->img_header.biHeight);
	
	for (size_t y = 0; y < h; y++)
	{
		free (img->img_pixels[y]);
	}
	free (img->img_pixels);
}

enum bmp_error
bmp_img_write (const bmp_img *img,
               const char    *filename)
{
	FILE *img_file = fopen (filename, "wb");
	
	if (img_file == NULL)
	{
		return BMP_FILE_NOT_OPENED;
	}
	
	// NOTE: This way the correct error code could be returned.
	const enum bmp_error err = bmp_header_write (&img->img_header, img_file);
	
	if (err != BMP_OK)
	{
		// ERROR: Could'nt write the header!
		fclose (img_file);
		return err;
	}
	
	// Select the mode (bottom-up or top-down):
	const size_t h = abs (img->img_header.biHeight);
	const size_t offset = (img->img_header.biHeight > 0 ? h - 1 : 0);
	
	// Create the padding:
	const unsigned char padding[3] = {'\0', '\0', '\0'};
	
	// Write the content:
	for (size_t y = 0; y < h; y++)
	{
		// Write a whole row of pixels to the file:
		fwrite (img->img_pixels[abs (offset - y)], sizeof (bmp_pixel), img->img_header.biWidth, img_file);
		
		// Write the padding for the row!
		fwrite (padding, sizeof (unsigned char), BMP_GET_PADDING (img->img_header.biWidth), img_file);
	}
	
	// NOTE: All good!
	fclose (img_file);
	return BMP_OK;
}

enum bmp_error
bmp_img_read (bmp_img    *img,
              const char *filename)
{
	FILE *img_file = fopen (filename, "rb");
	
	if (img_file == NULL)
	{
		return BMP_FILE_NOT_OPENED;
	}
	
	// NOTE: This way the correct error code can be returned.
	const enum bmp_error err = bmp_header_read (&img->img_header, img_file);
	
	if (err != BMP_OK)
	{
		// ERROR: Could'nt read the image header!
		fclose (img_file);
		return err;
	}
	
	bmp_img_alloc (img);
	
	// Select the mode (bottom-up or top-down):
	const size_t h = abs (img->img_header.biHeight);
	const size_t offset = (img->img_header.biHeight > 0 ? h - 1 : 0);
	const size_t padding = BMP_GET_PADDING (img->img_header.biWidth);
	
	// Needed to compare the return value of fread
	const size_t items = img->img_header.biWidth;
	
	// Read the content:
	for (size_t y = 0; y < h; y++)
	{
		// Read a whole row of pixels from the file:
		if (fread (img->img_pixels[abs (offset - y)], sizeof (bmp_pixel), items, img_file) != items)
		{
			fclose (img_file);
			return BMP_ERROR;
		}
		
		// Skip the padding:
		fseek (img_file, padding, SEEK_CUR);
	}
	
	// NOTE: All good!
	fclose (img_file);
	return BMP_OK;
}