I am noticing a large performance difference between Java & JOGL and C# & Tao.OpenGL when both loading PNGs from storage into memory, and when loading that BufferedImage (java) or Bitmap (C# - both are PNGs on hard drive) 'into' OpenGL.

This difference is quite large, so I assumed I was doing something wrong, however after quite a lot of searching and trying different loading techniques I've been unable to reduce this difference.

With Java I get an image loaded in 248ms and loaded into OpenGL in 728ms The same on C# takes 54ms to load the image, and 34ms to load/create texture.

The image in question above is a PNG containing transparency, sized 7200x255, used for a 2D animated sprite. I realise the size is really quite ridiculous and am considering cutting up the sprite, however the large difference is still there (and confusing).

On the Java side the code looks like this:

BufferedImage image = ImageIO.read(new File(fileName));
texture = TextureIO.newTexture(image, false);
texture.setTexParameteri(GL.GL_TEXTURE_MIN_FILTER, GL.GL_LINEAR);
texture.setTexParameteri(GL.GL_TEXTURE_MAG_FILTER, GL.GL_LINEAR);

The C# code uses:

Bitmap t = new Bitmap(fileName);

t.RotateFlip(RotateFlipType.RotateNoneFlipY);
Rectangle r = new Rectangle(0, 0, t.Width, t.Height);

BitmapData bd = t.LockBits(r, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

Gl.glBindTexture(Gl.GL_TEXTURE_2D, tID);
Gl.glTexImage2D(Gl.GL_TEXTURE_2D, 0, Gl.GL_RGBA, t.Width, t.Height, 0, Gl.GL_BGRA, Gl.GL_UNSIGNED_BYTE, bd.Scan0);
Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MIN_FILTER, Gl.GL_LINEAR);
Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MAG_FILTER, Gl.GL_LINEAR);

t.UnlockBits(bd);
t.Dispose();

After quite a lot of testing I can only come to the conclusion that Java/JOGL is just slower here - PNG reading might not be as quick, or that I'm still doing something wrong.

Thanks.

Edit2:

I have found that creating a new BufferedImage with format TYPE_INT_ARGB_PRE decreases OpenGL texture load time by almost half - this includes having to create the new BufferedImage, getting the Graphics2D from it and then rendering the previously loaded image to it.

Edit3: Benchmark results for 5 variations. I wrote a small benchmarking tool, the following results come from loading a set of 33 pngs, most are very wide, 5 times.

testStart: ImageIO.read(file) -> TextureIO.newTexture(image)  
result: avg = 10250ms, total = 51251  
testStart: ImageIO.read(bis) -> TextureIO.newTexture(image)  
result: avg = 10029ms, total = 50147  
testStart: ImageIO.read(file) -> TextureIO.newTexture(argbImage)  
result: avg = 5343ms, total = 26717  
testStart: ImageIO.read(bis) -> TextureIO.newTexture(argbImage)  
result: avg = 5534ms, total = 27673  
testStart: TextureIO.newTexture(file)  
result: avg = 10395ms, total = 51979

ImageIO.read(bis) refers to the technique described in James Branigan's answer below. argbImage refers to the technique described in my previous edit:

img = ImageIO.read(file);
argbImg = new BufferedImage(img.getWidth(), img.getHeight(), TYPE_INT_ARGB_PRE);
g = argbImg.createGraphics();
g.drawImage(img, 0, 0, null);
texture = TextureIO.newTexture(argbImg, false);

Any more methods of loading (either images from file, or images to OpenGL) would be appreciated, I will update these benchmarks.