Box Blur CGImageRef - iphone

Question

I'm attempting to implement a simple Box Blur, but am having issues. Namely, instead of blurring the images it seems to be converting each pixel to either: Red, Green, Blue or Black. Not sure exactly what is going on. Any help would be appreciated.
Please note, this code is simply a first pass to get it working, I'm not worried about speed... yet.
- (CGImageRef)blur:(CGImageRef)base radius:(int)radius {
CGContextRef ctx;
CGImageRef imageRef = base;
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = malloc(height * width *4);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(rawData, width, height,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);
char red = 0;
char green = 0;
char blue = 0;
for (int widthIndex = radius; widthIndex < width - radius; widthIndex++) {
for (int heightIndex = radius; heightIndex < height - radius; heightIndex++) {
red = 0;
green = 0;
blue = 0;
for (int radiusY = -radius; radiusY <= radius; ++radiusY) {
for (int radiusX = -radius; radiusX <= radius; ++radiusX) {
int xIndex = widthIndex + radiusX;
int yIndex = heightIndex + radiusY;
int index = ((yIndex * width) + xIndex) * 4;
red += rawData[index];
green += rawData[index + 1];
blue += rawData[index + 2];
}
}
int currentIndex = ((heightIndex * width) + widthIndex) * 4;
int divisor = (radius * 2) + 1;
divisor *= divisor;
int finalRed = red / divisor;
int finalGreen = green / divisor;
int finalBlue = blue / divisor;
rawData[currentIndex] = (char)finalRed;
rawData[currentIndex + 1] = (char)finalGreen;
rawData[currentIndex + 2] = (char)finalBlue;
}
}
ctx = CGBitmapContextCreate(rawData,
CGImageGetWidth( imageRef ),
CGImageGetHeight( imageRef ),
8,
CGImageGetBytesPerRow( imageRef ),
CGImageGetColorSpace( imageRef ),
kCGImageAlphaPremultipliedLast );
imageRef = CGBitmapContextCreateImage (ctx);
CGContextRelease(ctx);
free(rawData);
[(id)imageRef autorelease];
return imageRef;
}

Answer 1

The char colors should be declared as int.
int red = 0;
int green = 0;
int blue = 0;

Answer 2

I just have a comment. I used this script and it really works well and fast. the only thing is that it leaves the frame with width of radius which is not blurred. So I have modified it a bit so that it blurs whole area using mirroring technique near the edges.
For this one needs to put the following lines:
// Mirroring the part between edge and blur raduis
if (xIndex<0) xIndex=-xIndex-1; else if (xIndex>width-1) xIndex=2*width-xIndex-1;
if (yIndex<0) yIndex=-yIndex-1; else if (yIndex>height-1) yIndex=2*height-yIndex-1;
after these lines:
int xIndex = widthIndex + radiusX;
int yIndex = heightIndex + radiusY;
And then replace the headers of for loops:
for (int widthIndex = radius; widthIndex < width - radius; widthIndex++) {
for (int heightIndex = radius; heightIndex < height - radius; heightIndex++) {
with these headers:
for (int widthIndex = 0; widthIndex < width; widthIndex++) {
for (int heightIndex = 0; heightIndex < height; heightIndex++) {