Draw Text on a CVPixelBufferRef
The following code from apple (out of QTPixelBufferVCToCGImage) draws text to a CVPixelBufferRef with the name forgroundMask:
unsigned char* baseAddress; unsigned int rowbytes; unsigned int bytesPerRow; CGColorSpaceRef colorSpace = NULL; // lock the base address so we can paint on it, don't forget to release it in the end... . CVPixelBufferLockBaseAddress(foregroundMask,0); // get the base address of the pixel buffer (typecast into unsigned char for niceness). baseAddress = (unsigned char*)CVPixelBufferGetBaseAddress(foregroundMask); bytesPerRow = CVPixelBufferGetBytesPerRow(foregroundMask); // how many bytes per row do we have ? rowbytes = CVPixelBufferGetBytesPerRow(foregroundMask); colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB); // Draw some text on the image just for something to do DrawOnImage(baseAddress, bytesPerRow, maskWidth, maskHeight, colorSpace); CVPixelBufferUnlockBaseAddress(foregroundMask,0);
Where you have a function
static OSStatus DrawOnImage(void *inBaseAddress, size_t inRowBytes, size_t inWidth, size_t inHeight, CGColorSpaceRef inColorSpace)
{
CGContextRef theBitmapContext = NULL;
if (NULL == inBaseAddress || 0 == inRowBytes || 0 == inWidth || 0 == inHeight || NULL == inColorSpace) return paramErr;
theBitmapContext = CGBitmapContextCreate(inBaseAddress, inWidth, inHeight, 8, inRowBytes, inColorSpace, kCGImageAlphaPremultipliedFirst);
if (NULL == theBitmapContext) return kCGErrorFailure;
// what we want to draw
const char *string = {"Hello World"};
// some set up
CGContextSelectFont(theBitmapContext, "Arial-Black", 32, kCGEncodingMacRoman);
CGContextSetLineWidth(theBitmapContext, 1.5);
CGContextSetRGBStrokeColor(theBitmapContext, 0.0, 0.0, 0.0, 1.0); // black
CGContextSetRGBFillColor(theBitmapContext, 0.0, 1.0, 0.0, 1.0); // bright green
CGContextSetTextPosition(theBitmapContext, 10, 10);
CGContextSetTextDrawingMode(theBitmapContext, kCGTextFillStroke);
// draw it
CGContextShowText(theBitmapContext, string, strlen( string ));
if (NULL != theBitmapContext) CGContextRelease(theBitmapContext);
return noErr;
}