Take the following code as an example...
CIContext *context = [CIContext contextWithOptions:nil];
CIImage *inputImage = [[CIImage alloc] initWithImage:image];
CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
[filter setValue:inputImage forKey:kCIInputImageKey];
[filter setValue:[NSNumber numberWithFloat:5.0f] forKey:@"inputRadius"];
CIImage *result = [filter valueForKey:kCIOutputImageKey];
CGImageRef cgImage = [context createCGImage:result fromRect:[result extent]];
This results in the images you provided above. But if I instead use the original images rect to create the CGImage off of the context the resulting image is the desired size.
CGImageRef cgImage = [context createCGImage:result fromRect:[inputImage extent]];
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