How to resolve Error "EXC_BAD_ACCESS"

I am trying to resize an image on the basis of value selected on picker by user.

To this aim, I currently use following code:

- (UIImage *)scaleImage:(UIImage *)image toSize:(CGSize)targetSize {  

    CGRect frame;
    UIImage * newImage;
    newImage = image;

        frame = frontImageView.frame;
        frame.size.width = targetSize.width;
        frame.size.height = targetSize.height;
        frontImageView.frame = frame;



    // the pixels will be painted to this array




    CGImageRef imageRef = [newImage CGImage]; (APP crash at this point)
    CGFloat height = targetSize.height;
    CGFloat Width = targetSize.width;
    CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);


    pixels = (uint32_t *) malloc(targetSize.width * targetSize.height * sizeof(uint32_t));

    // clear the pixels so any transparency is preserved
    memset(pixels, 0, Width * height * sizeof(uint32_t));

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();


    alphaInfo = kCGImageA开发者_运维技巧lphaNoneSkipLast;

    CGContextRef bitmap =  CGBitmapContextCreate(pixels, Width, height, 8, Width * sizeof(uint32_t), colorSpace, 
                                                          kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);

    CGContextDrawImage(bitmap, CGRectMake(0, 0, Width, height), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);

    UIImage *result = [UIImage imageWithCGImage:ref];

    CGContextRelease(bitmap);
    CGImageRelease(ref);
    CGImageRelease(newImage);
    return result;  






}

If I resize an image, the first time (by 25 % for instance) there is no crash. But afterwards, a crash occurs with the error "exec_BAD_Access". How can I solve this?