iPhone-如何制作一个简单的精灵？

Question

I am new to iphone programming. I have two uiimageviews that have collisions. However, the images inside of them are not squares, so if one hits a corner, it detects a collision that doesnt exist between the two images. This is because UIImageViews are rectangles. Since I couldnt find a way to make no collision be detected if it hits a corner (a suggestion for this, if one exists, would be nice), I believe I should make two sprites instead of uiimageviews. I do not have Cocoa 2sd. I just have xcode 3.1. How do I declare a simple sprite and check for collision detectors between them?

Answer 1

The collisions on non transparent pixels would be inefficient using CoreGraphics.

You are better off investing in learning cocos2d and box 2d.

You would use beizer paths that you create around the sprite using a tool eg physics editor

These are then stored in a shapes file which holds the shapes of the sprites. They are then connected to sprites in cocos2d and collisions are done on the shapes that are in the background. You can turn on debug mode to see the shapes on screen.

This can be taken to the next level by assigning bit masks to the shapes and these on/off switches allow for eg choosing what happens when certain sprites collide with others (maybe trigger a different animation and sound effect for different shape collision pairs). One thing to not is it is important to try and box off your sprite shapes with beizer paths that have the least amount of vertices as the more there are the more checks are needed during runtime and your frame rate can drop.

In short, no it is not suitable to check for collisions on non transparent parts, even in cocos2d as each pixel is needed to be checked.

Answer 2

use this method

//For img_view1 rect //parameters are x,y,width,height

CGRect image_rect1 = CGRectMake(img_view1.position.x,img_view1.position.y,100,100);

//For img_view2 rect
//parameters are x,y,width,height

CGRect image_rect2 = CGRectMake(img_view2.position.x,img_view2.position.y,100,100)

Collision detection:

    if(CGRectIntersectsRect(image_rect1, image_rect2))
    {
        NSLog(@"Collision Example");
    }

however if you dont want to use CGRect for the views as you can simply use their respective frame properties.

-(BOOL)viewsDoCollide:(UIView *)view1 :(UIView *)view2{
    if(CGRectIntersectsRect(view1.frame, view2.frame))
    {
        return YES;
    }
    return NO;
}

but it would be great if you using cocoa2d

Answer 3

Please Try this code

#define imageWidth 40
#define imageHeight 60

UIImage *image1 = [UIImage imageNamed:@"firstimage.png"];
UIImage *image2 = [UIImage imageNamed: @"secondimage.png"];

CGSize itemSize = CGSizeMake(imageWidth, imageHeight);

UIGraphicsBeginImageContext(itemSize);

CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);
[image1 drawInRect:imageRect];
[image2 drawInRect:imageRect];

UIImage *overlappedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

The UIImage overlappedImage is a new image which contains the initial ones, overlapped. To be honest, I don't know if this is the best method to achieve this result, but I know it definitely works.