#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#pragma pack(1)

int adjust_brightness = 100; //-255 .. +255

typedef struct
{
    char signature[2];
    unsigned int fileSize;
    unsigned int reserved;
    unsigned int offset;
    unsigned int headerSize;
    unsigned int width;
    unsigned int height;
    unsigned short planeCount;
    unsigned short bitDepth;
    unsigned int compression;
    unsigned int compressedImageSize;
    unsigned int horizontalResolution;
    unsigned int verticalResolution;
    unsigned int numColors;
    unsigned int importantColors;

} BmpHeader;

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

        FILE *inFile,*outFile;
	long bytesPerLine;
        BmpHeader header;
	unsigned char *line;
        
        inFile = fopen( "aa.bmp", "rb" );
        if( !inFile ) {
		printf( "Error opening file %s.\n", argv[1] );
		return -1;
        }

        if( fread(&header, 1, sizeof(BmpHeader), inFile) != sizeof(BmpHeader) ) {
		printf( "Error reading bmp header.\n" );
		return -1;
        }

	bytesPerLine = (3 * (header.width + 1) / 4) * 4;

	outFile = fopen( "bb.bmp", "wb" );
        if( !outFile ) {
		printf( "Error opening outputfile.\n" );
		return -1;
        }

	
	fwrite(&header,1,sizeof(BmpHeader),outFile);

	line = new unsigned char[bytesPerLine];
	for (int i = 0; i < header.height; i++)
	{
		fread(line, 1, bytesPerLine, inFile);

		for (int j=0; j<bytesPerLine; j++) 
		{          		
			if (line[j]+adjust_brightness > 255) line[j]=255;
			else if (line[j]+adjust_brightness < 0) line[j]=0; 
			else line[j]=line[j]+adjust_brightness;
		}

	        fwrite(line, bytesPerLine, 1, outFile);
	}
        printf( "Done.\n" );
        fclose(inFile);
        fclose(outFile);

        printf( "\nBMP-Info:\n" );
        printf( "Width x Height: %i x %i\n", header.width, header.height );
        printf( "Depth: %i\n", (int)header.bitDepth );

	free(line);
        return 0;
}