Resize and crop images before displaying in UITableViewCells

Question

i have an UITableView in my app and i have to load some images that have a fixed width but different heights. I download the images async using an NSOperationQueue and for resiz

Answer 1

Try the following code. The createImage:image:width:height method requires a source CGImageRef and the new width and height of the final UIImage that will be returned. When using as source an UIImage, you can obtain the corresponding CGImageRef as follows:

UIImage *sourceImage;
CGImageRef *sourceRef = [sourceImage CGImage];

        // Draw the image into a pixelsWide x pixelsHigh bitmap and use that bitmap to 
        // create a new UIImage 
        - (UIImage *) createImage: (CGImageRef) image width: (int) pixelWidth height: (int) pixelHeight
        { 
            // Set the size of the output image 
            CGRect aRect = CGRectMake(0.0f, 0.0f, pixelWidth, pixelHeight); 
            // Create a bitmap context to store the new thumbnail 
            CGContextRef context = MyCreateBitmapContext(pixelWidth, pixelHeight); 
            // Clear the context and draw the image into the rectangle 
            CGContextClearRect(context, aRect); 
            CGContextDrawImage(context, aRect, image); 
            // Return a UIImage populated with the new resized image 
            CGImageRef myRef = CGBitmapContextCreateImage (context); 

            UIImage *img = [UIImage imageWithCGImage:myRef];

            free(CGBitmapContextGetData(context)); 
            CGContextRelease(context);
            CGImageRelease(myRef);

            return img; 
        } 



        // MyCreateBitmapContext: Source based on Apple Sample Code
        CGContextRef MyCreateBitmapContext (int pixelsWide,
                                            int pixelsHigh)
        {
            CGContextRef    context = NULL;
            CGColorSpaceRef colorSpace;
            void *          bitmapData;
            int             bitmapByteCount;
            int             bitmapBytesPerRow;

            bitmapBytesPerRow   = (pixelsWide * 4);
            bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

            colorSpace = CGColorSpaceCreateDeviceRGB();
            bitmapData = malloc( bitmapByteCount );
            if (bitmapData == NULL)
            {
                fprintf (stderr, "Memory not allocated!");
                CGColorSpaceRelease( colorSpace );
                return NULL;
            }
            context = CGBitmapContextCreate (bitmapData,
                                             pixelsWide,
                                             pixelsHigh,
                                             8,
                                             bitmapBytesPerRow,
                                             colorSpace,
                                             kCGImageAlphaPremultipliedLast);
            if (context== NULL)
            {
                free (bitmapData);
                CGColorSpaceRelease( colorSpace );
                fprintf (stderr, "Context not created!");
                return NULL;
            }
            CGColorSpaceRelease( colorSpace );

            return context;
        }