From: Xavier <xavier-list@...>
Date: 2006-05-29T16:12:04+09:00
Subject: PNG to OpenGL Texture (libpng)

Hi,
I'm trying to load a PNG file into an OpenGL texture using 
ruby-libpng-0.3.3
I can't quite figure out how to convert libpng data to the correct 
format.
I've dumped png.read_image to screen and it looks like my picture (with 
numbers instead of colors). At the moment I'm trying to use this index 
as my Red index (just to get something displaying) but am getting a 
white square instead. I'm already using textures for fonts, so I know 
that bit works.

Any Ideas?

As an aside, if anyone has a better x-platform way of doing this I'm all 
ears...

- Xavier

# Load a test png
rpng = Reader.new('res/img/test.png');

width, height, bit_depth, color_type,
interlace_type, compression_type, filter_type = rpng.get_IHDR

puts width # 20#for i in (0..height)
#  buffer += data[i].pack("C*")
#end
puts height # 20
puts bit_depth # 8
puts color_type # 6 .. not sure what this means yet
#for i in (0..height)
#  buffer += data[i].pack("C*")
#end
# Create and bind to OGL texture
@testogl = GL::GenTextures(1)[0];
GL.BindTexture(GL::TEXTURE_2D, @testogl);
GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_WRAP_S, GL::CLAMP);
GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_WRAP_T, GL::CLAMP);
GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MAG_FILTER,GL::LINEAR);
GL.TexParameteri(GL::TEXTURE_2D, GL::TEXTURE_MIN_FILTER,GL::LINEAR);

# Abomination follows
data = rpng.read_image
data2 = data.flatten
data3 = ""
for i in (0..data2.length-1)
data3 += " "
data3[i] = data2[i]
end

GL.TexImage2D(GL::TEXTURE_2D, 0, GL::RED, width,
              height, 0, GL::RED, GL::UNSIGNED_BYTE, data);

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