new module: intensity_transform (includes gamma correction, log transfomration, autoscaling, contrast stretching)

build error fix: remove trailing whitespaces, casting types

minor edits based on alalek's feedback

removing trailing whitespace

using std::array for LUT argument

modules/intensity_transform/include/opencv2/intensity_transform.hpp

@@ -0,0 +1,78 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+
+#ifndef OPENCV_INTENSITY_TRANSFORM_H
+#define OPENCV_INTENSITY_TRANSFORM_H
+
+#include "opencv2/core.hpp"
+
+/**
+ * @defgroup intensity_transform The module brings implementations of intensity transformation algorithms to adjust image contrast.
+ *
+ * Namespace for all functions is cv::intensity_trasnform.
+ *
+ * ### Supported Algorithms
+ * - Autoscaling
+ * - Log Transformations
+ * - Power-Law (Gamma) Transformations
+ * - Contrast Stretching
+ *
+ * Reference from following book and websites:
+ * - Digital Image Processing 4th Edition Chapter 3 [Rafael C. Gonzalez, Richard E. Woods] @cite Gonzalez2018
+ * - http://www.cs.uregina.ca/Links/class-info/425/Lab3/ @cite lcs435lab
+ * - https://theailearner.com/2019/01/30/contrast-stretching/ @cite theailearner
+*/
+
+namespace cv {
+namespace intensity_transform {
+
+//! @addtogroup intensity_transform
+//! @{
+
+/**
+ * @brief Given an input bgr or grayscale image and constant c, apply log transformation to the image
+ * on domain [0, 255] and return the resulting image.
+ *
+ * @param input input bgr or grayscale image.
+ * @param output resulting image of log transformations.
+*/
+CV_EXPORTS_W void logTransform(const Mat input, Mat& output);
+
+/**
+ * @brief Given an input bgr or grayscale image and constant gamma, apply power-law transformation,
+ * a.k.a. gamma correction to the image on domain [0, 255] and return the resulting image.
+ *
+ * @param input input bgr or grayscale image.
+ * @param output resulting image of gamma corrections.
+ * @param gamma constant in c*r^gamma where r is pixel value.
+*/
+CV_EXPORTS_W void gammaCorrection(const Mat input, Mat& output, const float gamma);
+
+/**
+ * @brief Given an input bgr or grayscale image, apply autoscaling on domain [0, 255] to increase
+ * the contrast of the input image and return the resulting image.
+ *
+ * @param input input bgr or grayscale image.
+ * @param output resulting image of autoscaling.
+*/
+CV_EXPORTS_W void autoscaling(const Mat input, Mat& output);
+
+/**
+ * @brief Given an input bgr or grayscale image, apply linear contrast stretching on domain [0, 255]
+ * and return the resulting image.
+ *
+ * @param input input bgr or grayscale image.
+ * @param output resulting image of contrast stretching.
+ * @param r1 x coordinate of first point (r1, s1) in the transformation function.
+ * @param s1 y coordinate of first point (r1, s1) in the transformation function.
+ * @param r2 x coordinate of second point (r2, s2) in the transformation function.
+ * @param s2 y coordinate of second point (r2, s2) in the transformation function.
+*/
+CV_EXPORTS_W void contrastStretching(const Mat input, Mat& output, const int r1, const int s1, const int r2, const int s2);
+
+//! @}
+
+}} // cv::intensity_transform::
+
+#endif