Method and apparatus for enhancing flash and ambient images
AssigneeMitsubishi Electric Research Laboratories, Inc.
InventorsRamesh Raskar, Amit Agrawal
Life of this patent
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Abstract
A method and system generate an enhanced output image. A first image is acquired of a scene illuminated by a first illumination condition. A second image is acquired of the scene illuminated by a second illumination condition. First and second gradient images are determined from the first and second images. Orientations of gradients in the first and second gradient images are compared to produce a combined gradient image, and an enhanced output image is constructed from the combined gradient image.
Claims15
A method for generating an enhanced output image, comprising the steps of:
- acquiring an ambient image of a scene illuminated by ambient light;
- acquiring a flash image of the scene illuminated with a flash unit;
- determining a gradient flash image from the flash image;
- determining a gradient ambient image from the ambient image;
- combining the gradient flash image and the gradient ambient image to produce a combined gradient image;
- constructing an enhanced output image from the combined gradient image;
- in which the flash image is due to a flash radiance Φ scaled by a flash power P, and the ambient image is due to an ambient radiance α scaled by an exposure time E, and wherein flash gradients in the gradient flash image are ∇Φ and ambient gradients in the gradient ambient image are ∇α;and
- in which a coherence map for the gradient flash image and the gradient ambient image is
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A system for generating an enhanced output image, comprising:
- a camera configured to acquire a first image of a scene illuminated by a first illumination condition and a second image of the scene illuminated by a second illumination condition;
- means for determining a first gradient image from the first image;
- means for determining a second gradient image from the second image;
- means for comparing the first gradient image and the second gradient image to produce a combined gradient image;
- means for constructing an enhanced output image from the combined gradient image;
- wherein the first illumination condition is produced by a flash unit, and the second illumination condition is ambient lighting;
- in which the first image is due to a flash radiance Φ scaled by a flash power P, and the second image is due to an ambient radiance α scaled by an exposure time E, and wherein flash gradients in the first gradient image are ∇Φ and ambient gradients in the second gradient image are ∇α;and
- in which a coherence map for the first gradient image and the second gradient image is
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A method for generating an enhanced output image, comprising the steps of:
- acquiring a first image of a scene illuminated by a first illumination condition;
- acquiring a second image of the scene illuminated by a second illumination condition;
- determining a first gradient image from the first image;
- determining a second gradient image from the second image;
- comparing an orientation of gradients in the first gradient image and the second gradient image to produce a combined gradient image;
- constructing an enhanced output image from the combined gradient image;
- in which the first illumination condition is produced by a flash unit and the second illumination condition is produced by ambient lighting;
- in which the first image is due to a flash radiance Φ scaled by a flash power P, and the second image is due to an ambient radiance α scaled by an exposure time E, and wherein flash gradients in the first gradient image are ∇Φ and ambient gradients in the second gradient image are ∇α;and
- wherein a coherence map for the first gradient image and the second gradient image is
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- Φ
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Dependencies are inferred from the claim text.