I am a freshman for IOS APP development, and I met a problem: " how to use vImage to convert an ARGB image to Gray image ". Actually, I have realized this conversion processing by other methods. However, I have found "vImage" could complete this work through "Accelerate Framework Reference". I have tried this method, but there is no any conversion result. Here, I attach the code, can you help me?
-(UIImage *)rgbTograyByvImage
{
const size_t width = self.size.width * self.scale;
const size_t height = self.size.height * self.scale;
const size_t bytesPerRow = width * 4;
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
CGContextRef bmContext= CGBitmapContextCreate(NULL, width, height, 8, bytesPerRow, space, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
CGColorSpaceRelease(space);
if (!bmContext) {
return nil;
}
CGContextDrawImage(bmContext, (CGRect){.origin.x = 0.0f, .origin.y = 0.0f, .size.width = width, .size.height = height}, self.CGImage);
UInt32 *data = (UInt32 *)CGBitmapContextGetData(bmContext);
if (!data) {
CGContextRelease(bmContext);
return nil;
}
int Aphal = 0;
int Red = 1;
int Green = 2;
int Blue = 3;
UInt8 *aphalSpace = malloc(sizeof(UInt8) * width * height);
UInt8 *redSpace = malloc(sizeof(UInt8) * width * height);
UInt8 *greenSpace = malloc(sizeof(UInt8) * width * height);
UInt8 *blueSpace = malloc(sizeof(UInt8) * width * height);
for (int y=0; y<height; y++) {
for (int x=0; x<width; x++) {
UInt8 *argbPixel = (UInt8 *) (&data[y*width+x]);
aphalSpace[y*width+x] = argbPixel[Aphal];
redSpace[y*width+x] = argbPixel[Red];
greenSpace[y*width+x] = argbPixel[Green];
blueSpace[y*width+x] = argbPixel[Blue];
}
}
vImage_Buffer argbImageBuffer = {(UInt8*)data, height, width, bytesPerRow};
vImage_Buffer aImageBuffer = {aphalSpace, height, width, width};
vImage_Buffer rImageBuffer = {redSpace, height, width, width};
vImage_Buffer gImageBuffer = {greenSpace, height, width, width};
vImage_Buffer bImageBuffer = {blueSpace, height, width, width};
vImage_Error error;
error = vImageConvert_ARGB8888toPlanar8(&argbImageBuffer, &aImageBuffer, &rImageBuffer, &gImageBuffer, &bImageBuffer, kvImageNoFlags);
if (error != kvImageNoError) {
NSLog(@"%s, vImage error %zd", __PRETTY_FUNCTION__, error);
}
CGImageRef grayImage = CGBitmapContextCreateImage(bmContext);
UIImage *gray = [UIImage imageWithCGImage:grayImage];
CGContextRelease(bmContext);
CGImageRelease(grayImage);
free(aphalSpace);
free(redSpace);
free(greenSpace);
free(blueSpace);
return gray;
}
