如何从两个图像创建UIImage：图片和边框

Question

i'm developing an iphone app , i need to manipulate a image at run time so that i can give it an image border .

i need to combine two UIImages , one as a border or background image , and the other UIImage will reside inside the first , so what's the best way to do it ??

i read about some functions like , UIGraphicsGetCurrentContext() but it seems that it should be done at main thread and i need some lighter code cause i need to call it several times .

thanks

Answer 1

Image Manipulation

Here's an example (not tested, just to show you an idea):

-(UIImage *)imageWithImage:(UIImage *)image borderImage:(UIImage *)borderImage covertToSize:(CGSize)size {
    UIGraphicsBeginImageContext(size);
    [borderImage drawInRect:CGRectMake( 0, 0, size.width, size.height )];
    [image drawInRect:CGRectMake( 10, 10, size.width - 20, size.height - 20)];
    UIImage *destImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return destImage;
}

It draws background image, than your image, which will be quite smaller. You can use this if you do want to really manipulate with image and your borderImage is not transparent. If it is transparent, you can draw it over your image (swap lines with drawRect: calls).

Just for Display

Or if you want this for display purpose only, you can overlay views or you can use Quartz and set some sort of border via CALayer.

self.imageView.layer.cornerRadius = 3.0;
self.imageView.layer.masksToBounds = YES;
self.imageView.layer.borderColor = [UIColor blackColor].CGColor;
self.imageView.layer.borderWidth = 1.0;

Answer 2

如果您的边框是透明的，您可以创建一个包含图像的UIImageView ，另一个包含边框的UIImageView ，然后将它们作为子视图添加到视图中，边框位于图像顶部。

Answer 3

你为什么不把第二个UIImageView作为第一个子视图（Border imageView）？

Answer 4

This is a piece of code I found way back when and use in my UIView extension. Not sure who to credit for it, but here it is:

- (UIImage *)overlayWithImage:(UIImage *)image2 {

    UIImage *image1 = self;
    CGRect drawRect = CGRectMake(0.0, 0.0, image1.size.width, image1.size.height);

    // Create the bitmap context
    CGContextRef    bitmapContext = NULL;
    void *          bitmapData;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;
    CGSize          size = CGSizeMake(image1.size.width, image1.size.height);

    // Declare the number of bytes per row. Each pixel in the bitmap in this
    // example is represented by 4 bytes; 8 bits each of red, green, blue, and
    // alpha.

        bitmapBytesPerRow   = (size.width * 4);
        bitmapByteCount     = (bitmapBytesPerRow * size.height);

    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.

        bitmapData = malloc( bitmapByteCount );

        if (bitmapData == NULL) {

            return nil;
        }

// Create the bitmap context. We want pre-multiplied ARGB, 8-bits
// per component. Regardless of what the source image format is
// (CMYK, Grayscale, and so on) it will be converted over to the format
// specified here by CGBitmapContextCreate.

        bitmapContext = CGBitmapContextCreate (bitmapData, size.width, size.height,8,bitmapBytesPerRow,                 CGColorSpaceCreateDeviceRGB(),kCGImageAlphaNoneSkipFirst);

        if (bitmapContext == NULL)

// error creating context

             return nil;

// Draw the image to the bitmap context. Once we draw, the memory
// allocated for the context for rendering will then contain the
// raw image data in the specified color space.

        CGContextDrawImage(bitmapContext, drawRect, [image1 CGImage]);
    CGContextDrawImage(bitmapContext, drawRect, [image2 CGImage]);
    CGImageRef   img = CGBitmapContextCreateImage(bitmapContext);
    UIImage*     ui_img = [UIImage imageWithCGImage: img];

    CGImageRelease(img);
    CGContextRelease(bitmapContext);
    free(bitmapData);

    return ui_img;
}

• I use this on a background thread without complications.