Creating UIImage from raw RGBA data

Our earlier tutorial, described how one can access RGBA data from a UIImage at any particular pixel coordinate.

The following code illustrates just the opposite – how does one go about constructing a UIImage from raw RGBA data.

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//
//Constructing RGBA data
//
/*height and width are integers denoting the dimensions of the image*/
unsigned char *rawData = malloc(width*height*4);

//populating rawData with pixel colour values and alpha information
for (int i=0; i<width*height;++i)
{
    rawData[4*i] = <red colour value>;
    rawData[4*i+1] = <green colour value>;
    rawData[4*i+2] = <blue colour value>;
    rawData[4*i+3] = 255; //alpha
}

/*
Once we have the raw data, we convert it into a UIImage.
The following code does the required work.
*/

CGDataProviderRef provider = CGDataProviderCreateWithData(NULL,rawData,width*height*4,NULL);

int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4*width;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

CGImageRef imageRef =
CGImageCreate(width,height,8,32,4*width,colorSpaceRef,bitmapInfo,provider,NULL,NO,renderingIntent);

UIImage *newImage = [UIImage imageWithCGImage:imageRef];

/*
newImage is the final image that is constructed from raw RGBA data.
Do remember to release the allocated parts.
*/

Please feel free to use this code in your projects.

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