DK-TM4C129X: image.pnm file is not support more than 256 color

Hi,

Please see below explanation. 

1. Load the file (File->Open).
2. Convert the image to indexed mode (Image->Mode->Indexed). Select “Generate optimum
palette” and select either 2, 16, or 256 as the maximum number of colors (for a 1 BPP, 4 BPP,
or 8 BPP image respectively). If the image is already in indexed mode, it can be converted to
RGB mode (Image->Mode->RGB) and then back to indexed mode.
3. Save the file as a PNM image (File->Save As). Select raw format when prompted.
4. Use pnmtoc to convert the PNM image into a C array.
This sequence will be the same for any source image type (GIF, BMP, TIFF, and so on); once loaded
into GIMP, it will treat all image types equally. For some source images, such as a GIF which is
naturally an indexed format with 256 colors, the second step could be skipped if an 8 BPP image is
desired in the application.

You can also refer to the source code at C:\ti\TivaWare_C_Series-2.2.0.295\tools\pnmtoc\pnmtoc.c file. 

//
// Is this a bitmap?
//
if(!bBitmap)
{
//
// No - get the number of distinct colors in the image.
//
GetNumColors(pui8Data + ui32Max, ui32Width, ui32Height, bMono);

//
// Determine how many colors are in the image.
//
if(g_ui32NumColors <= 2)
{
//
// There are 1 or 2 colors in the image, so encode it with 1 bit
// per pixel.
//
ui32Length = Encode1BPP(pui8Data + ui32Max, ui32Width, ui32Height,
bMono);
}
else if(g_ui32NumColors <= 16)
{
//
// There are 3 through 16 colors in the image, so encode it with
// 4 bits per pixel.
//
ui32Length = Encode4BPP(pui8Data + ui32Max, ui32Width, ui32Height,
bMono);
}
else if(g_ui32NumColors <= 256)
{
//
// There are 17 through 256 colors in the image, so encode it with
// 8 bits per pixel.
//
ui32Length = Encode8BPP(pui8Data + ui32Max, ui32Width, ui32Height,
bMono);
}
else
{
//
// There are more than 256 colors in the image, which is not
// supported.
//
fprintf(stderr, "%s: Image contains too many colors!\n",
basename(argv[0]));
return(1);
}
}

I see that pnm.c file but my image is more than 256 color how can convert pnm image to c array..

Hi,

  I think in GIMP you can save for 256 colors or less. 

in my image more color when I am creating 256 image index then image quality is down . I want to improve my image quality.
please any suggestions for the best quality image produces with c array. 

Hi,

 The pnmtoc utility only limits to 256 colors. Perhaps you can do Google search if there are any online tools that will convert your images to C array per your use case.