REMOVING ARTIFACTS FROM DOCUMENT IMAGES
First Claim
Patent Images
1. In a digital image editing environment, a method for removing artifacts from digital images, the method comprising:
- accessing a digital image;
calculating a shadow map for the digital image, the calculating including;
clustering pixel intensities of multiple blocks of the digital image into two or more clusters;
determining local background colors for each of the multiple blocks of the digital image based on the two or more clusters of each of the multiple blocks;
clustering pixel intensities representing the entire digital image into two or more clusters;
determining global background colors for the digital image based on the two or more clusters representing the entire digital image;
assigning a background color of the digital image as a global reference background color based at least in part on the determined global background colors; and
generating a per-pixel scaling factor to normalize the local background colors by the global reference background color, the per-pixel scaling factor mapping the local background colors of the digital image to the global reference background color; and
applying localized adjustment to pixels of the digital image to remove artifacts from the digital image using the per-pixel scaling factor.
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Abstract
Techniques for removing artifacts, such as shadows, from document images are described. A shadow map is generated for a digital image by first determining local background colors using clusters of local pixel intensities. Then, a global reference background color is selected from all pixel intensities of the digital image. Next, a per-pixel scaling factor is determined that maps the local background colors to the global reference background color, which applies localized adjustment to the digital image to remove local shadow.
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Citations
20 Claims
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1. In a digital image editing environment, a method for removing artifacts from digital images, the method comprising:
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accessing a digital image; calculating a shadow map for the digital image, the calculating including; clustering pixel intensities of multiple blocks of the digital image into two or more clusters; determining local background colors for each of the multiple blocks of the digital image based on the two or more clusters of each of the multiple blocks; clustering pixel intensities representing the entire digital image into two or more clusters; determining global background colors for the digital image based on the two or more clusters representing the entire digital image; assigning a background color of the digital image as a global reference background color based at least in part on the determined global background colors; and generating a per-pixel scaling factor to normalize the local background colors by the global reference background color, the per-pixel scaling factor mapping the local background colors of the digital image to the global reference background color; and applying localized adjustment to pixels of the digital image to remove artifacts from the digital image using the per-pixel scaling factor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A computing device comprising:
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one or more processors; and one or more computer-readable media having instructions stored thereon that, responsive to execution by the one or more processors, causes the one or more processors to implement a shadow removal module of an image editing application configured to perform operations comprising; accessing a digital image; dividing the digital image into multiple local blocks; clustering pixel intensities of each of the local blocks into two or more clusters, the two or more clusters corresponding at least to a graphics color and a background color within each of the local blocks; clustering pixel intensities of the entire digital image into two or more clusters corresponding to at least to a graphics color and a global background color of the digital image; determining a global reference background color from color intensities in the cluster corresponding to the global background color of the digital image by comparing the color intensities to a representative background color; generating a per-pixel scaling factor that maps pixels of the background colors in the local blocks to the global reference background color; and applying localized adjustment of color intensity to the pixels of the background colors in the local blocks to remove artifacts from the digital image using the per-pixel scaling factor. - View Dependent Claims (12, 13, 14, 15, 16)
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17. In a digital image editing environment, a method implemented by a computing device, the method comprising:
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accessing, by the computing device, a digital image in an image editing application; dividing, by the computing device, the digital image into multiple local blocks; generating, by the computing device, histograms for each of the multiple local blocks, the histograms representing a sample of a number of pixels of particular color intensities in each of the multiple local blocks; for each of the histograms of the multiple local blocks, using a Gaussian Mixture Model (GMM) by the computing device to cluster the histograms into two or more clusters; determining, by the computing device, pixels of the digital image that make up background intensities by upsampling pixels from one of the clusters of each of the multiple local blocks; generating, by the computing device, an aggregated histogram for multiple blocks of the digital image, the aggregated histogram representing a number of pixels of particular color intensities in all of the multiple blocks combined; using, by the computing device, the GMM to cluster the aggregated histogram into two or more clusters; determining, by the computing device, a global reference background color from the particular color intensities of the multiple blocks by comparing the each of the particular color intensities of the multiple blocks to a representative background color of the digital image; generating, by the computing device, a shadow map that comprises a per-pixel scaling factor that maps the pixels of the digital image that make up background intensities to the global reference background color; and applying, by the computing device, localized adjustment to the pixels of the digital image that make up background intensities to remove artifacts from the digital image using the per-pixel scaling factor. - View Dependent Claims (18, 19, 20)
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Specification