次の方法で画像をグレースケールに変換しようとしています。
#define bytesPerPixel 4
#define bitsPerComponent 8
-(unsigned char*) getBytesForImage: (UIImage*)pImage
{
CGImageRef image = [pImage CGImage];
NSUInteger width = CGImageGetWidth(image);
NSUInteger height = CGImageGetHeight(image);
NSUInteger bytesPerRow = bytesPerPixel * width;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = malloc(height * width * 4);
CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), image);
CGContextRelease(context);
return rawData;
}
-(UIImage*) processImage: (UIImage*)pImage
{
DebugLog(@"processing image");
unsigned char *rawData = [self getBytesForImage: pImage];
NSUInteger width = pImage.size.width;
NSUInteger height = pImage.size.height;
DebugLog(@"width: %d", width);
DebugLog(@"height: %d", height);
NSUInteger bytesPerRow = bytesPerPixel * width;
for (int xCoordinate = 0; xCoordinate < width; xCoordinate++)
{
for (int yCoordinate = 0; yCoordinate < height; yCoordinate++)
{
int byteIndex = (bytesPerRow * yCoordinate) + xCoordinate * bytesPerPixel;
//Getting original colors
float red = ( rawData[byteIndex] / 255.f );
float green = ( rawData[byteIndex + 1] / 255.f );
float blue = ( rawData[byteIndex + 2] / 255.f );
//Processing pixel data
float averageColor = (red + green + blue) / 3.0f;
red = averageColor;
green = averageColor;
blue = averageColor;
//Assigning new color components
rawData[byteIndex] = (unsigned char) red * 255;
rawData[byteIndex + 1] = (unsigned char) green * 255;
rawData[byteIndex + 2] = (unsigned char) blue * 255;
}
}
NSData* newPixelData = [NSData dataWithBytes: rawData length: height * width * 4];
UIImage* newImage = [UIImage imageWithData: newPixelData];
free(rawData);
DebugLog(@"image processed");
return newImage;
}
したがって、画像を変換したいときは、processImage を呼び出すだけです。
imageToDisplay.image = [self processImage: image];
しかし、imageToDisplay は表示されません。何が問題なのですか?
ありがとう。