Image quality metric for HDR images and video
AssigneeDolby Laboratories Licensing Corporation
InventorsRobert Wanat, Robin Atkins, Anustup Kumar Atanu Choudhury, Scott Daly, Jaclyn Anne Pytlarz
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Abstract
Methods and systems for generating an image quality metric are described. A reference and a test image are first converted to the ITP color space. After calculating difference images ΔI, ΔT, and ΔP, using the color channels of the two images, the difference images are convolved with low pass filters, one for the I channel and one for the chroma channels (I or P). The image quality metric is computed as a function of the sum of squares of filtered ΔI, ΔT, and ΔP values. The chroma low-pass filter is designed to maximize matching the image quality metric with subjective results.
Claims16
A method for generating an image quality metric using color differences, the method comprising:
- receiving input mages comprising a reference image and a test mage;
- converting the reference image and the test image to an ITP reference image and an ITP test image in the ITP color space;
- generating difference images ΔI, ΔT, and ΔP by subtracting corresponding pixel values in the ITP reference image and the ITP test image for the I, T, and P color channels;
- filtering the ΔI difference image with an intensity low-pass filter to generate a filtered ΔI image (FΔI);
- filtering the ΔT and ΔP difference images with a chroma low-pass filter to generate filtered ΔT and ΔP images (FΔT and FΔP);
- generating sums of squared values based on corresponding pixel values of the filtered ΔI, ΔT and ΔP images;
- and
- generating the image quality metric as a function of the sums of squared values.
A method for generating an image quality metric using color differences, the method comprising:
- receiving input images comprising a reference image and a test image;
- converting the reference image and the test image to an ITP reference image and an ITP test image in the ITP color space;
- filtering the intensity components of the ITP reference image and the ITP test image with an intensity low-pass filter to generate a filtered intensity reference image and a filtered intensity test image;
- filtering the T and P chroma components of the ITP reference image and the ITP test image with a chroma low-pass filter to generate filtered T and P chroma reference images and filtered T and P chroma test images;
- generating difference images FΔI, and FΔT, and FΔP by subtracting corresponding pixel values in the filtered I, and P reference images and the filtered I, T, and P reference test images;
- generating sums of squared values based on corresponding pixel values of the FΔI, FΔT, and FΔP images;
- and
- generating the image quality metric as a function of the sums of squared values.
Dependencies are inferred from the claim text.