Abstract
This paper proposes an automatic image correction method for portrait photographs, which promotes consistency of facial skin color by suppressing skin color changes due to background colors. In portrait photographs, skin color is often distorted due to the lighting environment (e.g., light reflected from a colored background wall and over-exposure by a camera strobe). This color distortion is emphasized when artificially synthesized with another background color, and the appearance becomes unnatural. In our framework, we, first, roughly extract the face region and rectify the skin color distribution in a color space. Then, we perform color and brightness correction around the face in the original image to achieve a proper color balance of the facial image, which is not affected by luminance and background colors. Our color correction process attains natural results by using a guide image, unlike conventional algorithms. In particular, our guided image filtering for the color correction does not require a perfectly-aligned guide image required in the original guide image filtering method proposed by He et al. Experimental results show that our method generates more natural results than conventional methods on not only headshot photographs but also natural scene photographs. We also show automatic yearbook style photo generation as another application.
Highlights
Portrait photographs sometimes get undesirable color due to a background color reflection
In addition to the algorithm described in this paper, we propose a hybrid guided image filtering (GIF) method, which performs color transfer on the local face region while keeping colors in other regions, making GIF suitable for the correction of facial skin color and brightness
We proposed a facial skin color correction method in combination with color grading and guided image filtering
Summary
Portrait photographs sometimes get undesirable color due to a background color reflection. There is a need for a simple and automatic method not requiring any special technique to unify the color and brightness between multiple images. The undesirable color on portrait photographs is caused by the following: Licensee MDPI, Basel, Switzerland. We define foreground, background, and original image, respectively, as fi , bi , and yi (different from that in (5)). Α works as the blending rate, and called alpha-mat. The background replacement with another background z is given by yi0 := fi + αi zi . Our algorithm generates the yearbook style photos from the original images using the target image
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