What can I use instead of NSBitmapImageRep in iOS? (Water ripples example)

I found this interesting post about water ripple simulation. It includes a Xcode project with a little cocoa app for OSX. I tried to get the app running in iOS using Swift, but I couldn't find a solution to the following problem:

The OSX app uses NSBitmapImageRep to draw bitmap data from an array onto the screen (this happens in the BBRippleView.m). Unfortunately, NSBitmapImageRep is not available in iOS. I tried using a CGImage instead, which is "kind of working": I can see some kind of water ripples, but they are split up in some weird way and they don't move the way they are supposed to. I guess the CGImage expects to get the bitmap data in a different format than it currently gets it.

Edit: Here is my iOS RippleView class: RippleView.swift

Edit 2: Modified RippleView.swift

What would be the right way to implement the following OSX code segments in iOS using Swift?

        image = [[NSImage alloc] initWithSize:NSMakeSize(cols, rows)];
        bufrep = [[NSBitmapImageRep alloc]
                            initWithBitmapDataPlanes:NULL
                            pixelsWide:cols
                            pixelsHigh:rows
                            bitsPerSample:8
                            samplesPerPixel:1
                            hasAlpha:NO
                            isPlanar:YES
                            colorSpaceName:NSDeviceWhiteColorSpace
                            bytesPerRow:0
                            bitsPerPixel:0];
        [image addRepresentation:bufrep];

And

-(void)applyBuffer
{
    unsigned char* data = [bufrep bitmapData];
    int x = 0;
    int y = 0;
    int position = 0;
    for ( y = 0; y < rows; y ++) {
        for ( x = 0; x < cols ; x ++) {
            position = (y * cols) + x;
            data[position] = (char)buffer2[position] << 1;
        }           
    }       
}

You are telling CGImageCreate that your image is greyscale, with 8 bits by pixel. But your buffers are arrays of Ints, which are either 32 or 64 bits (4 or 8 bytes).

Switch to UInt8, that should help a lot.