How do you animate a sprite sheet?

[Austin]

I know how to animate individual .png's but how would you take one png (spritesheet) and then animate it?

[Austin]

anyone?

[jtara]

Maybe they don't know what you are asking?

[Upsidedowndog]

Originally Posted by jtara

Maybe they don't know what you are asking?

I think I can clarify this - I used to use Sprite Sheets all the time in games years ago, and they're commonly used in console games. Basically it's a single graphic made up of a grid. Each box of the grid contains one state of a graphic sprite or an animation frame, say all the possible states of a character walking. In order to animate this, the graphic is either masked in the view and its top-left coordinate changed to match the top-left coordinate of the appropriate grid box so that the image in that box appears within the masked area, or the area of a particular box in the grid is copied to a new bitmap and displayed itself.

I am actually planning on using this technique for a current project, but haven't yet gotten the module built, so as much of an explanation as I can provide, I'm actually no help right now! Sorry!

[gibtang]

Originally Posted by Austin

anyone?

This is how I do it
1 - Use CGRectMake to make a rect (The area where I want to draw 1 sprite from the sprite sheet)
2 - Use CGContextSaveGState to save the current context
3 - Use CGContextClipToRect to clip the context to the rect in #1
4 - Use drawAtPoint to draw my UIImage

[gibtang]

It is best that you play around with the X,Y coordinates so that you can see how the clipping works

[Austin]

Originally Posted by gibtang

This is how I do it
1 - Use CGRectMake to make a rect (The area where I want to draw 1 sprite from the sprite sheet)
2 - Use CGContextSaveGState to save the current context
3 - Use CGContextClipToRect to clip the context to the rect in #1
4 - Use drawAtPoint to draw my UIImage

Thanks for the help! I knew there was a way to do this.

[gibtang]

Originally Posted by Austin

Thanks for the help! I knew there was a way to do this.

No problem, sprite sheet and sprite clipping was what I used a long time ago when I was doing J2ME mobile game dev when space was at a premium, but with iPhone. I have pretty much abandoned it and just put in 1 sprite per UIImage. It makes coding a lot easier for me.

[Austin]

This is more difficult than I thought. I'm trying to crop the image using CGRectMake, here is my code...

UIImage *spriteImage = [UIImage imageNamed:@"spritesheet.png"];
	
sprite.image = spriteImage;	
	
sprite.frame = CGRectMake(110.0, 180.0, 100.0, 100.0);