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Translate CGContext to orient the image correctly #5

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Translate CGContext to orient the image correctly #5

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9 changes: 8 additions & 1 deletion 15-core-image-filters/15-core-image-filters.md
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Expand Up @@ -129,11 +129,18 @@ a new method which enables rescaling an image with interpolation disabled:
// Render the CIImage into a CGImage
CGImageRef cgImage = [[CIContext contextWithOptions:nil] createCGImage:image fromRect:image.extent];

CGFloat size = image.extent.size.width * scale;

// Now we'll rescale using CoreGraphics
UIGraphicsBeginImageContext(CGSizeMake(image.extent.size.width * scale, image.extent.size.width * scale));
UIGraphicsBeginImageContext(CGSizeMake(size, size));
CGContextRef context = UIGraphicsGetCurrentContext();
// We don't want to interpolate (since we've got a pixel-correct image)
CGContextSetInterpolationQuality(context, kCGInterpolationNone);

//make sure it's in the correct orientation
CGContextTranslateCTM(context, 0, size);
CGContextScaleCTM(context, 1.0, -1.0);

CGContextDrawImage(context, CGContextGetClipBoundingBox(context), cgImage);
// Get the image out
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
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