Getting RGB values for each pixel from a 24bpp Bitmap for conversion to GBA format in C

Question

I want to read the RGB values for each pixel from a .bmp file, so I can convert the bmp into a format suitable for GBA (GameBoy Advance).

I

Answer 1

You need first to get the number of colors available in the embedded palette. This is available in the DIB Header.

Then you can read all color components that contain the palette.

You can see all header information like offset to know whereto seek : http://en.wikipedia.org/wiki/BMP_file_format.

This should work: (Edit: Add code to write in file)

FILE *inFile, *outFile;
BMPHeader header;
BMPImageInfo info;
RGB *palette, *p;
int i = 0;

inFile = fopen("C://in.bmp", "rb");
if( !inFile )
   return;

if( fread(&header, sizeof(BMPHeader), 1, inFile) != 1 )
   return; // Manage error and close file

if( fread&info, sizeof(BMPImageInfo), 1, inFile) != 1 )
   return; // Manage error and close file

if( info.numColors > 0 )
{
   palette = (RGB*)malloc(sizeof(RGB) * info.numColors);
   if( fread(palette, sizeof(RGB), info.numColors, inFile) != info.numColors )
      return; // manage error and close file
}

fclose(inFile)

// Binary method => if read later by another computer
outFile = fopen("path", "wb");
if( !outFile )
   return;

if( fwrite(&info.numColors, sizeof(unsigned int), 1, outFile) != 1 )
   return; // Manage Error and close file

if( fwrite(&palette, sizeof(RGB), info.numColors, outFile) != info.numColors )
   return; // Manage error and close file

fclose(outFile);

// Text method => if read later by human
outFile = fopen("path", "w");
if( !outFile )
   return;

for( i=0; ired, p->green, p->blue) < 0 )
      return; // Manage error and close file
}

fclose(outFile);