PNG8 + PicoPNG

Monkey Forums/Monkey Programming/PNG8 + PicoPNG

AdamRedwoods

(Posted 2013) [#1]

At some point i'd like to see PNG8 (4-bit png) support, since for mobile this uses less memory (GL_UNSIGNED_SHORT_4_4_4_4). might be faster, too.

i was able to get PicoPng working for GLFW and loading PNG8 color indexed files, after it converted them to RGB32:
http://lodev.org/lodepng/

Nice and small, fits easily into stbimage, and license is good. Something to think about.

Cpp code to interface to stb_image (swap out the stbi_load_from_file for png):


#include <iostream>
#include <fstream>

extern "C" unsigned char* loadPicoPNG(FILE* f, int *width, int *height, int *depth, int req_comp );

unsigned char* loadPicoPNG(FILE* f, int *width, int *height, int *depth, int req_comp ) //designed for loading files from hard disk in an std::vector
{

  std::vector<unsigned char>  buffer ;
  std::vector<unsigned char>  *image = new std::vector<unsigned char> ;
  
   unsigned char buffer_start[129];
   unsigned long buflen = sizeof(unsigned char) ;
   
  while (!feof(f)) {
		
	int n = fread(buffer_start, buflen, 128, f);

	  if(n > 0)
	  {
		for (int i=0; i<n; i++) {
			buffer.push_back(buffer_start[i]);
		}
	  }

  }
 
  int error = decodePNG(*image, (unsigned long&)*width, (unsigned long&)*height, (unsigned long&)*depth, buffer.empty() ? 0 : &buffer[0], (unsigned long)buffer.size(), true);

  *depth = 4; //*depth /2;

  std::cout << "w/h " << *width <<"  "<<*height << "  "<< *depth <<std::endl;
  //if there's an error, display it
  if(error != 0) std::cout << "error: " << error << std::endl;

  return &(*image)[0];
}

EDIT: sorry, not drag-n-drop, i forgot i modded picopng to return the image depth.

EDIT2: ahh, it's in Android. I don't see it in iOS. ok, maybe this is only needed for GLFW!