iPhone:How to crop image in ios5

问题

In my application the requirement is to grab image from the photo library or camera and if user wants to crop the image then he should be able to do it but I do not have any idea how to crop the image fetched from camera or photo library.

if you have any idea then share it...

回答1:

You can crop your image by using UIGraphicsGetImageFromCurrentImageContext

The idea is to draw your image to a cropped graphic context using CoreGraphics and then exporting the current context to an image.

UIGraphicsGetImageFromCurrentImageContext Returns an image based on the contents of the current bitmap-based graphics context.

Return A image object containing the contents of the current bitmap graphics context.

Try something like that :

- (UIImage*)imageCrop:(UIImage *)imageToCrop toRect:(CGRect)rect
{
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef currentContext = UIGraphicsGetCurrentContext();

    CGRect clippedRect = CGRectMake(0, 0, rect.size.width, rect.size.height);
    CGContextClipToRect( currentContext, clippedRect);

    CGRect drawRect = CGRectMake(rect.origin.x, rect.origin.y, imageToCrop.size.width, imageToCrop.size.height);
    CGContextDrawImage(currentContext, drawRect, imageToCrop.CGImage);
    UIImage *cropped = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return cropped;
}

hope this helps, Vincent

回答2:

I have done the same thing in Mac, probably you could try that out,

+(NSImage *)BreakImageForFirstImage:(NSImage *)pSrcImage Size:(NSSize)imageSize{

    /*
     Create a new NSImage with the size of the subrect, lock focus on it, draw the sub rect of the source image into
     the new, locked image using -drawInRect:fromRect:operation:fraction: ("fromRect:" should be the subrect of the 
     source; the first rect argument will be a rect of the same size as the subrect, with a 0,0 origin), then unlock 
     focus from the new image. Done. Because of all that's involved in this, it might still be more efficient just to 
     load individual images  

     */


    NSSize srcSize = [pSrcImage size];

    int subImageHeight = imageSize.height;
    int subImageWidth = imageSize.width;

    NSRect subImageRect = NSMakeRect(0,0,imageSize.width,imageSize.height);

    NSRect tempRect = NSMakeRect(0,0,imageSize.width,imageSize.height);

    //NSMutableArray *pImageArray = [[NSMutableArray alloc]initWithCapacity:noOfImages];

    NSImage *pTempImage = nil;
    int rowId =0;
    int colId = 0;
    //for(;rowId<noOfRow;rowId++)
    {
        pTempImage = [[NSImage alloc]initWithSize:imageSize];
        tempRect = NSMakeRect(rowId*subImageWidth,colId*subImageHeight,subImageWidth,subImageHeight);
        [pTempImage lockFocus];
        [pSrcImage drawInRect:subImageRect fromRect:tempRect operation:NSCompositeSourceOver fraction:1.0];
        [pTempImage unlockFocus];
        //[pImageArray insertObject:pTempImage atIndex:rowId];

    }

    return pTempImage;
    /* */
}

May be at some places , you might need to convert NS to UI to make it run for iOS

来源：https://stackoverflow.com/questions/9578821/iphonehow-to-crop-image-in-ios5