Hiding a part of an image in iPhone-Game

I am working on a small game, in which the user can 开发者_StackOverflow社区drag rows and columns of images to solve a puzzle. The puzzle does not use the whole screen, the "puzzle area" is in a rectangle area from 0,160 to 320,480.

Now, if the user drags a column of the images up, the top image in that column would be displayed "out of" that puzzle area. How could I only have that portion of the image shown, that remains within the puzzle area. Like not showing the whole 50x50 Pixel of the image, but only the lower 40x50 Pixel etc.?

You just need to set the frames on your views properly. If your puzzle views frame ends at the (0,160) point on top, any subviews you've added to it; such as the puzzle pieces will be hidden when they move out of the frame.

Hopefully I'm not oversimplifying the problem, but one of the easier ways I can think of working this scenario is by maintaining a proper view structure while moving the puzzle pieces.

i.e. as long as the view on the top half of the screen is higher up on the view hierarchy than the puzzle pieces (you could ensure this by properly maintaining the subviews), the puzzle pieces will be hidden under the top view if they move beneath it.

Is this what you need?

Cheers.

I am just tryin to give u some ideas.. Hope u can implement with that...

First use touchesBegan and touchesMoved methods to detect how much pixels the image has been dragged. Simultaneously u can also move the frame of the image to a new coordinate , hiding a portion of the image....tat is out of puzzle area.....

Hope this helps....

myImageView.frame=CGRectMake(0,0,50,50);

Let the above one be the actual frame. Now u have received the amt of pixels thru which the user has moved the image from touches method. Let it be some y1. To hide a part of the imageview reframe the imageview like this ,

  myImageView.frame=CGRectMake(0,-y1,50,50);

negative y1 since u want to move out of the screen.. Hope this helps.