Error using sepia image effect in iOS? - ios

Question

In my app, I am having an imageView, the image in the imageView should be give some effects like sepia, black and white.
To do sepia effect I used the following code,
-(UIImage*)makeSepiaScale:(UIImage*)image
{
CGImageRef cgImage = [image CGImage];
CGDataProviderRef provider = CGImageGetDataProvider(cgImage);
CFDataRef bitmapData = CGDataProviderCopyData(provider);
UInt8* data = (UInt8*)CFDataGetBytePtr(bitmapData);
int imagWidth = image.size.width;
int imageheight = image.size.height;
NSInteger myDataLength = imagWidth * imageheight * 4;
for (int i = 0; i < myDataLength; i+=4)
{
UInt8 r_pixel = data[i];
UInt8 g_pixel = data[i+1];
UInt8 b_pixel = data[i+2];
int outputRed = (r_pixel * .393) + (g_pixel *.769) + (b_pixel * .189);
int outputGreen = (r_pixel * .349) + (g_pixel *.686) + (b_pixel * .168);
int outputBlue = (r_pixel * .272) + (g_pixel *.534) + (b_pixel * .131);
if(outputRed>255)outputRed=255;
if(outputGreen>255)outputGreen=255;
if(outputBlue>255)outputBlue=255;
data[i] = outputRed;
data[i+1] = outputGreen;
data[i+2] = outputBlue;
}
CGDataProviderRef provider2 = CGDataProviderCreateWithData(NULL, data, myDataLength, NULL);
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * imagWidth;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGImageRef imageRef = CGImageCreate(imagWidth, imageheight, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider2, NULL, NO, renderingIntent);
CGColorSpaceRelease(colorSpaceRef); // YOU CAN RELEASE THIS NOW
CGDataProviderRelease(provider2); // YOU CAN RELEASE THIS NOW
CFRelease(bitmapData);
UIImage *sepiaImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef); // YOU CAN RELEASE THIS NOW
return sepiaImage;
}
It is working perfectly, but only for .png image, when I use .jpg images, it just displays a black colour view for the imageView. Any help will be appreciated

Answer 1

Use core image processing,
-(void)makeSepiaScale
{
CIImage *beginImage =[[CIImage alloc]initWithImage:imageForView];
CIContext * context=[CIContext contextWithOptions:nil];
CIFilter *filter = [CIFilter filterWithName:#"CISepiaTone"
keysAndValues: kCIInputImageKey, beginImage,
#"inputIntensity", #0.8, nil];
CIImage *outImage = [filter outputImage];
CGImageRef cgimg=[context createCGImage:outImage fromRect:[outImage extent]];
[imageView setImage:[UIImage imageWithCGImage:cgimg]];
}

Answer 2

Use CGImageCreateWithJPEGDataProvider to get the bitmap from JPEG:
-(UIImage*)makeSepiaScale:(UIImage*)image {
CGImageRef cgJpegImage = [image CGImage];
CGDataProviderRef jpegProvider = CGImageGetDataProvider(cgJpegImage);
CGImageRef cgBitmapImage = CGImageCreateWithJPEGDataProvider(jpegProvider, nil, NO, kCGRenderingIntentRelativeColorimetric);
CGDataProviderRef bitmapProvider = CGImageGetDataProvider(cgBitmapImage);
CFDataRef bitmapData = CGDataProviderCopyData(bitmapProvider);
UInt8* data = (UInt8*)CFDataGetBytePtr(bitmapData);
// other code to make sepia effect
}
You can't use JPEG encoded image like plain RGB. So, just decode it with CGImageCreateWithJPEGDataProvider first.

Answer 3

I suspect you are dealing with non RGBA format data .... JPG for one does not have an Alpha channel. Rather than deal with the intricacies of the data I suggest that you consider using Core Image filters, I've used them with jpg and PNG without any issues.
There is a variety of Core Image filters including one for Sepia and another for grayscale / black and white here is the code for Sepia:
-(UIImage*)makeSepiaScale:(UIImage*)input_image output:(UIImage *)output
{
CIImage *cimage = [[CIImage alloc] initWithImage:input_image];
CIFilter *myFilter = [CIFilter filterWithName:#"CISepiaTone"];
[myFilter setDefaults];
[myFilter setValue:cimage forKey:#"inputImage"];
[myFilter setValue:[NSNumber numberWithFloat:0.8f] forKey:#"inputIntensity"];
CIImage *image = [myFilter outputImage];
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef cgImage = [context createCGImage:image fromRect:image.extent];
output = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);
return (output);}
PS the Apple documentation on CoreImage is good, I suggest you read up on it.