java game images loading very slowly

Question

I am trying to develop a game that imports the background images from a [100][100] matrix. The matrix will hold int values to correlate to what should be drawn on the backg

Answer 1

It is not obvious what SpriteSheet#grabImage(...) does. But I'm pretty sure that there is some call to BufferedImage#getSubImage(...) involved. Is that right?

If this is right, there are two potential issues here:

1. When you are loading an image with ImageIO, the type of the resulting image is not known. By "type" I refer to the BufferedImage#getType(). This type may be BufferedImage.TYPE_CUSTOM, particularly when it is a PNG with transparency. When an image with this type is painted, then this painting is awfully slow, because there are some color conversions done internally.

2. When you call BufferedImage#getSubImage(...), then the image on which you call this method will become "unmanaged". That means that the actual image data can no longer be held directly in video memory. (There are some very involved technical details behind that one. And these details may change between different JRE versions. For example, they changed between Java 6 and Java 7. However, the rule of thumb is: If you want to draw images with high performance, don't call BufferedImage#getSubImage(...) on the image that you want to paint)

The solution for both issues can be to convert the images into managed images of the type BufferedImage.TYPE_INT_ARGB. So for each image that you want to paint, you can call

BufferedImage toPaint = convertToARGB(originalImage);

with this method:

public static BufferedImage convertToARGB(BufferedImage image)
{
    BufferedImage newImage = new BufferedImage(
        image.getWidth(), image.getHeight(),
        BufferedImage.TYPE_INT_ARGB);
    Graphics2D g = newImage.createGraphics();
    g.drawImage(image, 0, 0, null);
    g.dispose();
    return newImage;
}

In your example, you could apply this to your grass and tree images.

Another (maybe even more important) issue is that you seem to be drawing your tiles scaled: You seem to paint a 64x64 pixels sprite with a size of 32x32. If this is correct, then you could consider rescaling the input image once, and then drawing the tiles with their original size of 32x32.

In any case, it's hard to predict how much speedup each of these changes will actually bring, but they should be worth a try.