How to crop the image in iPhone

问题

I want to do the same thing as asked in this question. In my App i want to crop the image like we do image cropping in FaceBook can any one guide me with the link of good tutorial or with any sample code. The Link which i have provided will completely describe my requirement.

回答1:

You may create new image with any properties. Here is my function, witch do that. you just need to use your own parameters of new image. In my case, image is not cropped, I just making some effect, moving pixels from there original place to another. But if you initialize new image with another height and width, you can just copy from any range of pixels of old image you need, to new one:

-(UIImage *)Color:(UIImage *)img
{
    int R;
    float m_width = img.size.width;
    float m_height = img.size.height;
    if (m_width>m_height) R = m_height*0.9;
    else R = m_width*0.9;
    int m_wint = (int)m_width;      //later,  we will need this parameters in float and int. you may just use "(int)" and "(float)" before variables later, and do not implement another ones
    int m_hint = (int)m_height;

    CGRect imageRect;
    //cheking image orientation. we will work with image pixel-by-pixel, so we need to make top side at the top.
    if(img.imageOrientation==UIImageOrientationUp 
       || img.imageOrientation==UIImageOrientationDown) 
    {
        imageRect = CGRectMake(0, 0, m_wint, m_hint); 
    }
    else 
    {
        imageRect = CGRectMake(0, 0, m_hint, m_wint); 
    }
    uint32_t *rgbImage = (uint32_t *) malloc(m_wint * m_hint * sizeof(uint32_t));
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(rgbImage, m_wint, m_hint, 8, m_wint *sizeof(uint32_t), colorSpace,   kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
    CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
    CGContextSetShouldAntialias(context, NO);
    CGContextTranslateCTM(context, 0, m_hint);
    CGContextScaleCTM(context, 1.0, -1.0);
    switch (img.imageOrientation) {
        case UIImageOrientationRight:
        {
            CGContextRotateCTM(context, M_PI / 2);
            CGContextTranslateCTM(context, 0, -m_wint);            
        }break;
        case UIImageOrientationLeft:
        {
            CGContextRotateCTM(context, - M_PI / 2);
            CGContextTranslateCTM(context, -m_hint, 0);            
        }break;
        case UIImageOrientationUp:
        {
            CGContextTranslateCTM(context, m_wint, m_hint);
            CGContextRotateCTM(context, M_PI);
        }
        default:
            break;
    }

    CGContextDrawImage(context, imageRect, img.CGImage);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    //here is new image. you can change m_wint and m_hint as you whant
    uint8_t *result = (uint8_t *) calloc(m_wint * m_hint * sizeof(uint32_t), 1);
    for(int y = 0; y < m_hint; y++) //new m_hint here
    {
        float fy=y;
        double yy =    (m_height*(  asinf(m_height/(2*R))-asin(((m_height/2)-fy)/R)   )) /
        (2*asin(m_height/(2*R))); // (xx, yy) - coordinates of pixel of OLD image
        for(int x =  0; x < m_wint; x++) //new m_wint here
        {
            float fx=x;
            double xx =    (m_width*(  asin(m_width/(2*R))-asin(((m_width/2)-fx)/R)   )) /
            (2*asin(m_width/(2*R)));
            uint32_t rgbPixel=rgbImage[(int)yy * m_wint + (int)xx];
            int intRedSource = (rgbPixel>>24)&255;
            int intGreenSource = (rgbPixel>>16)&255;
            int intBlueSource = (rgbPixel>>8)&255;
            result[(y * (int)m_wint + x) * 4] = 0;
            result[(y * (int)m_wint + x) * 4 + 1] = intBlueSource;
            result[(y * (int)m_wint + x) * 4 + 2] = intGreenSource;
            result[(y * (int)m_wint + x) * 4 + 3] = intRedSource;

        }
    }

    free(rgbImage);

    colorSpace = CGColorSpaceCreateDeviceRGB();
    context = CGBitmapContextCreate(result, m_wint, m_hint, 8, m_wint * sizeof(uint32_t), colorSpace,   kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast  ); //new m_wint and m_hint as well


    CGImageRef image1 = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    UIImage *resultUIImage = [UIImage imageWithCGImage:image1];
    CGImageRelease(image1);


    @try {
        free(result);
    }
    @catch (NSException * e) {
        NSLog(@"proc. Exception: %@", e);
    }

    return resultUIImage;
}

回答2:

CGRect rectImage = CGRectMake(p1.x,p1.y, p2.x - p1.x, p4.y - p1.y);

//Create bitmap image from original image data,
//using rectangle to specify desired crop area

CGImageRef imageRef = CGImageCreateWithImageInRect([imageForCropping CGImage], rectImage); 
UIImage *croppedImage = [UIImage imageWithCGImage:imageRef]; 
imageView1 = [[UIImageView alloc] initWithFrame:CGRectMake(p1.x, p1.y,p2.x-p1.x p4.y-p1.y)];
imageView1.image = croppedImage;
[self.view addSubview:imageView1];
CGImageRelease(imageRef);

来源：https://stackoverflow.com/questions/7950719/how-to-crop-the-image-in-iphone