working copy

algorithm not working and has checked

5 files changed, 497 insertions, 45 deletions

diff --git a/camera_calib.c b/camera_calib.c
index 4b03a12..b55f954 100644
--- a/camera_calib.c
+++ b/camera_calib.c
@@ -488,7 +488,7 @@ static void init_undistort_map_scalar(struct cam_calib_data_t *data) {
 	float dist_radial, dist_tang_x, dist_tang_y, dist_x, dist_y;
 	float _x, _y, _y_sq, _x_sq, r_sq;
 	float x_corr, y_corr;
-	struct lense_undistort_coord_t *map;
+	struct coord_t *map;
 	const int scale_fact = (1 << (data->calib_map_scale_fact));
 	float x_resolution_scaling, y_resolution_scaling;		// camera_matrix needs to be scaled depending on the camera resolution
 	
@@ -541,8 +541,8 @@ static void init_undistort_map_scalar(struct cam_calib_data_t *data) {
 			x_corr = fx*dist_x + cx - fov_x_start;
 			y_corr = fy*dist_y + cy - fov_y_start;
 			
-			map->coord_x = (int)roundf(x_corr*scale_fact);
-			map->coord_y = (int)roundf(y_corr*scale_fact);
+			map->x = (int)roundf(x_corr*scale_fact);
+			map->y = (int)roundf(y_corr*scale_fact);
 			map++;
 		}
 	}
@@ -700,7 +700,7 @@ static void calib_scalar(struct cam_calib_data_t *data) {
 	int x_corr, y_corr;
 	void *img_calib, *img_uncalib; 
 	int bit_channel;
-	struct lense_undistort_coord_t *map;
+	struct coord_t *map;
 	const int scale_fact = data->calib_map_scale_fact;
 	const int is_color = data->is_color;
 	
@@ -718,8 +718,8 @@ static void calib_scalar(struct cam_calib_data_t *data) {
 	for(v = fov_y_start; v <= fov_y_end; v++) {
 		for(u = fov_x_start; u <= fov_x_end; u++) {
 			
-			x_corr = map->coord_x;
-			y_corr = map->coord_y;
+			x_corr = map->x;
+			y_corr = map->y;
 			map++;
 			
 			if(bit_channel <= 8) {
diff --git a/color_pipe.c b/color_pipe.c
index 0b77c61..648e259 100644
--- a/color_pipe.c
+++ b/color_pipe.c
@@ -2,9 +2,7 @@
 * @file			main.cpp
 * @brief		Color Image Processing Pipeline with O-3000 USB camera
 * @author		Patrick Roth - roth@stettbacher.ch
-* @version		1.0
-* @date			2015-02-10
-* @copyright	2012-2016 Stettbacher Signal Processing AG
+* @copyright	Stettbacher Signal Processing AG
 * 
 * @remarks
 *
@@ -365,12 +363,12 @@ static void set_default_value(struct color_pipe_t *pipe) {
 	pipe->debayer_data.alg_new = pipe->debayer_data.alg;
 	
 	pipe->awb_data.enable = 0;
-	pipe->awb_data.gray_threshold = 0.3;
+	pipe->awb_data.gray_threshold = 0.3f;
 	pipe->awb_data.gray_threshold_new = pipe->awb_data.gray_threshold;
-	pipe->awb_data.ctrl_k = 0.01;
+	pipe->awb_data.ctrl_k = 0.01f;
 	pipe->awb_data.ctrl_k_new = pipe->awb_data.ctrl_k;
-	pipe->awb_data.gain_red = 1.0;
-	pipe->awb_data.gain_blue = 1.0;
+	pipe->awb_data.gain_red = 1.0f;
+	pipe->awb_data.gain_blue = 1.0f;
 	
 	pipe->cam_calib_data.enable = 0;
 	pipe->cam_calib_data.lense = O3000_LS_F2_8;
@@ -385,16 +383,23 @@ static void set_default_value(struct color_pipe_t *pipe) {
 	memcpy(pipe->color_calib_data.a, ccm_presets[pipe->color_calib_data.ccm], sizeof(pipe->color_calib_data.a));
 	
 	pipe->sharp_data.enable = 0;
-	pipe->sharp_data.sharp_factor = 5.0;
+	pipe->sharp_data.sharp_factor = 5.0f;
 	pipe->sharp_data.sharp_factor_new = pipe->sharp_data.sharp_factor;
 	pipe->sharp_data.sharp_alg = SHARP_ALG_LOCAL;
 	pipe->sharp_data.sharp_alg_new = pipe->sharp_data.sharp_alg;
-	pipe->sharp_data.local_sens = 94.0;
+	pipe->sharp_data.local_sens = 94.0f;
 	pipe->sharp_data.local_sens_new = pipe->sharp_data.local_sens_new;
 	
 	pipe->gamma_data.enable = 0;
-	pipe->gamma_data.gamma = 1.2;
+	pipe->gamma_data.gamma = 1.2f;
 	pipe->gamma_data.gamma_new = pipe->gamma_data.gamma;
+	
+	pipe->trapcorr_data.enable = 0;
+	pipe->trapcorr_data.map_init = 0;
+	pipe->trapcorr_data.wv = 1.0f;
+	pipe->trapcorr_data.wh = 1.0f;
+	pipe->trapcorr_data.wv_new = pipe->trapcorr_data.wv;
+	pipe->trapcorr_data.wh_new = pipe->trapcorr_data.wh;
 }
 
 
@@ -458,7 +463,7 @@ void __stdcall color_pipe_process(struct color_pipe_t *__restrict__ color_pipe,
 	
 #ifdef DEBUG_PROC_TIME
 	uint64_t ts_start = get_ts();
-	uint64_t ts_debayer, ts_awb, ts_calib, ts_ccm, ts_sharp, ts_gamma;
+	uint64_t ts_debayer, ts_awb, ts_calib, ts_ccm, ts_sharp, ts_gamma, ts_trapcorr;
 #endif // DEBUG_PROC_TIME
 	
 	/*
@@ -676,6 +681,41 @@ void __stdcall color_pipe_process(struct color_pipe_t *__restrict__ color_pipe,
 	
 	
 	/*
+	 * Pipeline stage: Isosceles trapezoid correction
+	 */
+	if(color_pipe->trapcorr_data.enable) {
+		
+		// auto-reinit perspective correction map if image format, resolution or weights have changed
+		if(	color_pipe->trapcorr_data.bit_channel	!= bit_channel	||
+			color_pipe->trapcorr_data.width			!= width		||
+			color_pipe->trapcorr_data.height		!= height		||
+			color_pipe->trapcorr_data.wv			!= color_pipe->trapcorr_data.wv_new ||
+			color_pipe->trapcorr_data.wh			!= color_pipe->trapcorr_data.wh_new) {
+			
+			color_pipe->trapcorr_data.map_init = 0;
+		}
+		
+		// apply user parameter (double buffered)
+		color_pipe->trapcorr_data.wv = color_pipe->trapcorr_data.wv_new;
+		color_pipe->trapcorr_data.wh = color_pipe->trapcorr_data.wh_new;
+		
+		color_pipe->trapcorr_data.img_in = img_out;
+		color_pipe->trapcorr_data.is_color = is_color;
+		color_pipe->trapcorr_data.bit_channel = bit_channel;
+		color_pipe->trapcorr_data.width = width;
+		color_pipe->trapcorr_data.height = height;
+		
+		trapcorr(&(color_pipe->trapcorr_data));
+		
+		img_out = color_pipe->trapcorr_data.img_out;
+	}
+#ifdef DEBUG_PROC_TIME
+	ts_trapcorr = get_ts();
+#endif // DEBUG_PROC_TIME
+	
+	
+	
+	/*
 	 * Return processed image depending on active pipeline stages.
 	 */
 	color_pipe->img_out = img_out;
@@ -692,6 +732,7 @@ void __stdcall color_pipe_process(struct color_pipe_t *__restrict__ color_pipe,
 	printf("        color correction:       %lld msec\n", ts_ccm - ts_calib);
 	printf("        sharpening:             %lld msec\n", ts_sharp - ts_ccm);
 	printf("        gamma:                  %lld msec\n", ts_gamma - ts_sharp);
+	printf("        trapeze correction:     %lld msec\n", ts_trapcorr - ts_sharp);
 #endif // DEBUG_PROC_TIME
 }
 
@@ -834,6 +875,42 @@ void __stdcall color_pipe_stageconf_gamma(struct color_pipe_t *color_pipe, int e
 
 
 /**
+ * Pipeline stage configuration: Isosceles Trapeze Correction
+ * 
+ * The vertical and horizontal correction weight are positive
+ * numbers starting from 0. A weight of 1.0 means no correction. A weight lesser than
+ * 1.0 means the upper trapeze line is shorter than the lower trapeze line.
+ * Therfore a weight greater than 1.0 means the upper trapeze line is longer than
+ * the lower line.
+ * 
+ * @param color_pipe Pointer to pipeline context
+ * @param enable not 0: enable, 0: disable
+ * @param wv vertical weight 
+ * @param wh horizontal weight
+ */
+void __stdcall color_pipe_stageconf_trapcorr(struct color_pipe_t *color_pipe, int enable, float wv, float wh) {
+	// paranoia
+	if(color_pipe == NULL) {
+		printf("%s: Pipeline pointer is NULL!\n", __func__);
+		return;
+	}
+	
+	// range check
+	if(wv < 0.0f) {
+		wv = 0.0f;
+	}
+	if(wh < 0.0f) {
+		wh = 0.0f;
+	}
+	
+	color_pipe->trapcorr_data.enable = enable;
+	color_pipe->trapcorr_data.wv_new = wv;
+	color_pipe->trapcorr_data.wh_new = wh;	
+	color_pipe->trapcorr_data.map_init = 0;
+}
+
+
+/**
  * Open color image processing pipeline.
  * This function allocates memory for various pipe algorithm. The pipeline is set up for a maximum possible image size defined
  * by the height, width and bitdepth per color channel.
@@ -927,7 +1004,7 @@ int __stdcall color_pipe_open(struct color_pipe_t **color_pipe, const int max_im
 		goto _pipe_open_abort;
 	}
 	data->cam_calib_data.calib_map = do_aligned_alloc(ALIGNMENT_SIZE,
-														sizeof(struct lense_undistort_coord_t)*max_img_height*max_img_width,
+														sizeof(struct coord_t)*max_img_height*max_img_width,
 														__func__, __LINE__-1);
 	if(data->cam_calib_data.calib_map == NULL) {
 		goto _pipe_open_abort;
@@ -977,6 +1054,19 @@ int __stdcall color_pipe_open(struct color_pipe_t **color_pipe, const int max_im
 		goto _pipe_open_abort;
 	}
 	
+	// allocate memory for isosceles trapeze correction algorithm
+	data->trapcorr_data.img_out = do_aligned_alloc(ALIGNMENT_SIZE, max_img_size, __func__, __LINE__-1);
+	if(data->trapcorr_data.img_out == NULL) {
+		goto _pipe_open_abort;
+	}
+	data->trapcorr_data.map = do_aligned_alloc(ALIGNMENT_SIZE,
+											   sizeof(struct coord_t)*max_img_height*max_img_width,
+											   __func__, __LINE__-1);
+	if(data->trapcorr_data.map == NULL) {
+		goto _pipe_open_abort;
+	}
+	
+	// set suitable  and valid defaults
 	set_default_value(data);
 	*color_pipe = data;
 	
@@ -1022,6 +1112,8 @@ int __stdcall color_pipe_close(struct color_pipe_t *data) {
 	do_aligned_free(data->sharp_data.sharp_mask);
 	do_aligned_free(data->gamma_data.img_gamma);
 	do_aligned_free(data->gamma_data.gamma_table);
+	do_aligned_free(data->trapcorr_data.img_out);
+	do_aligned_free(data->trapcorr_data.map);
 	
 	// free various image buffers
 	free(data);
diff --git a/color_pipe.h b/color_pipe.h
index 2833d0f..b4c50da 100644
--- a/color_pipe.h
+++ b/color_pipe.h
@@ -2,9 +2,7 @@
 * @file			color_pipe.h
 * @brief		Color Processing Pipeline Definitions
 * @author		Patrick Roth - roth@stettbacher.ch
-* @version		1.0
-* @date			2016-03-01
-* @copyright	2012-2016 Stettbacher Signal Processing AG
+* @copyright	Stettbacher Signal Processing AG
 * 
 * @remarks
 *
@@ -36,6 +34,15 @@
 
 
 /**
+ * Coordinate definition.
+ */
+struct coord_t {
+	int x;			///< x-coordinate of calibrated pixel
+	int y;			///< y-coordinate of calibrated pixel
+};
+
+
+/**
  * demosaicing algorithm definition
  */
 enum bayer_alg_t {
@@ -55,7 +62,7 @@ struct debayer_data_t {
 	enum enumDataFormat_t format;			///< data format of input image
 	enum enumBayerPattern_t start_pattern;	///< first pixel starts with this bayer pattern
 	enum bayer_alg_t alg;					///< debayer algorithm type
-	enum bayer_alg_t alg_new;				///< this debayer algorithm type is changed by API call (use double buffering concept)
+	enum bayer_alg_t alg_new;				///< this debayer algorithm type is changed by API call (use double buffering)
 };
 
 
@@ -71,9 +78,9 @@ struct awb_data_t {
 	int width;						///< image width in number of pixels
 	int16_t *img_yuv;				///< Image buffer holding YUV image. This buffer must be allocated externly.
 	float gray_threshold;			///< gray value threshold
-	float gray_threshold_new;		///< this gray value threshold is changed by API call (use double buffering concept)
+	float gray_threshold_new;		///< this gray value threshold is changed by API call (use double buffering)
 	float ctrl_k;					///< controller gain
-	float ctrl_k_new;				///< this controller gain is changed by API call (use double buffering concept)
+	float ctrl_k_new;				///< this controller gain is changed by API call (use double buffering)
 	float gain_red;					///< red color gain
 	float gain_blue;				///< blue color gain
 };
@@ -131,19 +138,6 @@ enum o3000_lenses_t {
 
 
 /**
- * Lense undistortion coordinate definition.
- * This coordinate pair defines the undistorted pixel location.
- * 
- * NOTE The pixel location may lay between a pixel pair. Therefore this coordinates are
- * scaled by a defined factor defined at @ref cam_calib_data_t.
- */
-struct lense_undistort_coord_t {
-	int coord_x;			///< x-coordinate of calibrated pixel
-	int coord_y;			///< y-coordinate of calibrated pixel
-};
-
-
-/**
  * camera calibration structure
  * 
  * The total width @ref tot_width and height @ref tot_height define the image size take during calibration processs.
@@ -164,10 +158,23 @@ struct cam_calib_data_t {
 	struct dist_coeff_t dist_coeff;			///< distortion coefficients
 	struct camera_matrix_t camera_matrix;	///< camera matrix
 	enum o3000_lenses_t lense;				///< lense type
-	enum o3000_lenses_t lense_new;			///< lense type is changed by API call (use double buffering concept)
+	enum o3000_lenses_t lense_new;			///< lense type is changed by API call (use double buffering)
 	int undistort_map_init;					///< flag indicating if lens undistortion map is initialized
-	struct lense_undistort_coord_t *calib_map;	///< Lense undistortion map. This buffer must be allocated externly.
-	int calib_map_scale_fact;				///< Bit shifts applied on undistortion map.
+	
+	/**
+	 * Lense undistortion map.
+	 * A coordinate pair defines the undistorted pixel location. It may be shifted (see @ref calib_map_scale_fact).
+	 * 
+	 * This buffer must be allocated externly.
+	 */ 
+	struct coord_t *calib_map;
+	
+	/**
+	 * Bit shift applied on undistortion map @ref calib_map.
+	 * The pixel location may lay between a pixel pair. Therefore the coordinates defined at the undistortion map
+	 * @ref calib_map are (scaled) shifted by this factor.
+	 */ 
+	int calib_map_scale_fact;
 };
 
 
@@ -218,7 +225,7 @@ struct color_calib_data_t {
 	int height;								///< image height in number of pixels
 	float a[3][3];							///< 3x3 color correction matrix
 	enum ccm_preset_t ccm;					///< color correction matrix type loaded
-	enum ccm_preset_t ccm_new;				///< this color correction matrix type is changed by API call (use double buffering concept)
+	enum ccm_preset_t ccm_new;				///< this color correction matrix type is changed by API call (use double buffering)
 };
 
 
@@ -244,11 +251,11 @@ struct sharp_data_t {
 	int height;								///< image height in number of pixels
 	int16_t *img_yuv;						///< YUV image buffer. This buffer must be allocated externly.
 	float sharp_factor;						///< Sharpening factor: As higher as stronger sharpening is done.
-	float sharp_factor_new;					///< this sharpening factor is changed by API call (use double buffering concept)
+	float sharp_factor_new;					///< this sharpening factor is changed by API call (use double buffering)
 	enum sharp_alg_t sharp_alg;				///< sharpening algorithm type
-	enum sharp_alg_t sharp_alg_new;			///< this algorithm type is changed by API call (use double buffering concept)
+	enum sharp_alg_t sharp_alg_new;			///< this algorithm type is changed by API call (use double buffering)
 	float local_sens;						///< Sensitivity setting of local sharpening algorithm in per cent. 100 % means everything is sharpened like the global algorithm does
-	float local_sens_new;					///< this sensitivity setting is changed by API call (use double buffering concept)
+	float local_sens_new;					///< this sensitivity setting is changed by API call (use double buffering)
 	int16_t *img_yuv_sharp;					///< YUV image buffer holding sharpened Y-channel. This buffer must be allocated externly.
 	int16_t *img_sobel;						///< Sobel image in YUV color space used by local sharpening algorithm. This buffer must be allocated externly.
 	int16_t *img_gauss;						///< Gaussian low-pass filtered image in YUV color space used by local sharpening algorithm. This buffer must be allocated externly.
@@ -268,7 +275,7 @@ struct gamma_data_t {
 	int width;								///< image width in number of pixels
 	int height;								///< image height in number of pixels
 	float gamma;							///< gamma coefficient
-	float gamma_new;						///< this gamma coefficient is changed by API call (use double buffering concept)
+	float gamma_new;						///< this gamma coefficient is changed by API call (use double buffering)
 	int gamma_table_bitdepth;				///< gamma table is initialized with this bit-depth 
 	float gamma_table_init;					///< gamma table is initialized with this coefficient 
 	int *gamma_table;						///< Lookup table containg gamma corrected value.  This buffer must be allocated externly.
@@ -276,6 +283,41 @@ struct gamma_data_t {
 
 
 /**
+ * Isosceles trapezoid correction definition
+ */
+struct trapcorr_data_t {
+	int enable;								///< flag to enable this algorithm
+	void *img_out;							///< Isosceles corrected output image. This buffer must be allocated externly.
+	void *img_in;							///< Input image.
+	int is_color;							///< Not 0 if it's a color image
+	int bit_channel;						///< Bits per color channel.
+	int width;								///< image width in number of pixels
+	int height;								///< image height in number of pixels
+	float wv;								///< vertical correction weight in per cent (NOTE not implemented yet!)
+	float wh;								///< horizontal correction weight in per cent
+	float wv_new;							///< this vertical correction weight in per cent is changed by API call (use double buffering) (NOTE not implemented yet!)
+	float wh_new;							///< this horizontal correction weight in per cent is changed by API call (use double buffering)
+	 
+	int map_init;							///< flag indicating perspective correction map is initialized
+	
+	/**
+	 * perspective correction map
+	 * A coordinate pair defines the pixel location to be corrected. It may be shifted (see @ref map_scale_fact).
+	 * 
+	 * This buffer must be allocated externly.
+	 */
+	struct coord_t *map;
+	
+	/**
+	 * Bit shift applied on correction map @ref map.
+	 * The pixel location may lay between a pixel pair. Therefore the coordinates defined at the correction map
+	 * @ref map are (scaled) shifted by this factor.
+	 */
+	int map_scale_fact;
+};
+
+
+/**
  * Color pipe definition structure holding all memory data from different pipeline
  * stages. This structure and image buffers are allocated dynamically.
  */
@@ -293,6 +335,7 @@ struct color_pipe_t {
 	struct color_calib_data_t color_calib_data;		///< color calibration data used for color corretion
 	struct sharp_data_t sharp_data;					///< image sharpening data
 	struct gamma_data_t gamma_data;					///< gamma correction data
+	struct trapcorr_data_t trapcorr_data;			///< isosceles trapezoid correction data
 };
 
 
@@ -312,6 +355,7 @@ void __stdcall color_pipe_stageconf_cam_calib(struct color_pipe_t *color_pipe, i
 void __stdcall color_pipe_stageconf_color_calib(struct color_pipe_t *color_pipe, int enable, enum ccm_preset_t ccm_preset);
 void __stdcall color_pipe_stageconf_sharp(struct color_pipe_t *color_pipe, int enable, float factor, enum sharp_alg_t alg, float sens);
 void __stdcall color_pipe_stageconf_gamma(struct color_pipe_t *color_pipe, int enable, float gamma);
+void __stdcall color_pipe_stageconf_trapcorr(struct color_pipe_t *color_pipe, int enable, float wv, float wh);
 
 #if defined(__cplusplus) || defined(c_plusplus)
 } // extern "C"
diff --git a/color_pipe_private.h b/color_pipe_private.h
index f5a48f8..b2954ac 100644
--- a/color_pipe_private.h
+++ b/color_pipe_private.h
@@ -47,6 +47,8 @@ int sharpening(struct sharp_data_t *sharp_data);
 
 int gamma_corr(struct gamma_data_t *gamma_data);
 
+int trapcorr(struct trapcorr_data_t *trapcorr_data);
+
 #if defined(__cplusplus) || defined(c_plusplus)
 } // extern "C"
 #endif
diff --git a/trapcorr.c b/trapcorr.c
new file mode 100644
index 0000000..3ace25f
--- /dev/null
+++ b/trapcorr.c
@@ -0,0 +1,314 @@
+/**
+* @file			trapcorr.c
+* @brief		isosceles trapeze correction algorithm
+* @author		Patrick Roth - roth@stettbacher.ch
+* @copyright	Stettbacher Signal Processing AG
+* 
+* @remarks
+*
+* <PRE>
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public
+* License as published by the Free Software Foundation; either
+* version 2.1 of the License, or (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public
+* License along with this library; if not, write to the Free Software
+* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+* </PRE>
+*
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+
+#include "color_pipe_private.h"
+
+
+
+/**
+ * Pixel value interpolation of RGB image (8 bit per color channel).
+ * If a pixel coordinate with a fraction part is of interest, do interpolate the correct value from their neighbor's pixel.
+ * 
+ * E. g. the pixel coordinate x/y = 1.8/2.3 gives the following weights:
+ *          +------+------+
+ *          |      |      |
+ *          | 14%  | 56%  |		14% = 20%*70%, 56% = 80%*70%
+ *          |      |      |
+ *          +------+------+
+ *          |      |      |
+ *          | 6%   | 24%  |		6% = 20%*30%, 24% = 80%*30%
+ *          |      |      |
+ *          +------+------+
+ * 
+ * The weights are applied to the neighors and the resulting pixel value is saved at the given location.
+ * 
+ * NOTE
+ * The input and output image must have the same pixel size.
+ * 
+ * @param img_out On return: image with interpolated values
+ * @param x saved interpolated pixel value at this x-coordinate
+ * @param y saved interpolated pixel value at this y-coordinate
+ * @param height image height of input and output image in number of pixels
+ * @param width image width of input and output image in number of pixels
+ * @param img_in input image to interpolate pixel values
+ * @param coord_x x-coordinate to interpolate
+ * @param coord_y y-coordinate to interpolate
+ * @param scale_fact coordinates are scaled by this factor
+ */
+static void interpolate_rgb8_scalar(uint8_t *img_out, const int x, const int y, const int height, const int width,
+						 const uint8_t *img_in, const int coord_x, const int coord_y, const int scale_fact)
+#include "alg_interpolate_rgb_scalar.h"
+
+
+/**
+ * Pixel value interpolation of RGB image (16 bit per color channel).
+ * If a pixel coordinate with a fraction part is of interest, do interpolate the correct value from their neighbor's pixel.
+ * 
+ * E. g. the pixel coordinate x/y = 1.8/2.3 gives the following weights:
+ *          +------+------+
+ *          |      |      |
+ *          | 14%  | 56%  |		14% = 20%*70%, 56% = 80%*70%
+ *          |      |      |
+ *          +------+------+
+ *          |      |      |
+ *          | 6%   | 24%  |		6% = 20%*30%, 24% = 80%*30%
+ *          |      |      |
+ *          +------+------+
+ * 
+ * The weights are applied to the neighors and the resulting pixel value is saved at the given location.
+ * 
+ * NOTE
+ * The input and output image must have the same pixel size.
+ * 
+ * @param img_out On return: image with interpolated values
+ * @param x saved interpolated pixel value at this x-coordinate
+ * @param y saved interpolated pixel value at this y-coordinate
+ * @param height image height of input and output image in number of pixels
+ * @param width image width of input and output image in number of pixels
+ * @param img_in input image to interpolate pixel values
+ * @param coord_x x-coordinate to interpolate
+ * @param coord_y y-coordinate to interpolate
+ * @param scale_fact coordinates are scaled by this factor
+ */
+static void interpolate_rgb16_scalar(uint16_t *img_out, const int x, const int y, const int height, const int width,
+						  const uint16_t *img_in, const int coord_x, const int coord_y, const int scale_fact)
+#include "alg_interpolate_rgb_scalar.h"
+
+
+/**
+ * Pixel value interpolation of monochrome image (8 bit per pixel).
+ * If a pixel coordinate with a fraction part is of interest, do interpolate the correct value from their neighbor's pixel.
+ * 
+ * E. g. the pixel coordinate x/y = 1.8/2.3 gives the following weights:
+ *          +------+------+
+ *          |      |      |
+ *          | 14%  | 56%  |		14% = 20%*70%, 56% = 80%*70%
+ *          |      |      |
+ *          +------+------+
+ *          |      |      |
+ *          | 6%   | 24%  |		6% = 20%*30%, 24% = 80%*30%
+ *          |      |      |
+ *          +------+------+
+ * 
+ * The weights are applied to the neighors and the resulting pixel value is saved at the given location.
+ * 
+ * NOTE
+ * The input and output image must have the same pixel size.
+ * 
+ * @param img_out On return: image with interpolated values
+ * @param x saved interpolated pixel value at this x-coordinate
+ * @param y saved interpolated pixel value at this y-coordinate
+ * @param height image height of input and output image in number of pixels
+ * @param width image width of input and output image in number of pixels
+ * @param img_in input image to interpolate pixel values
+ * @param coord_x x-coordinate to interpolate
+ * @param coord_y y-coordinate to interpolate
+ * @param scale_fact coordinates are scaled by this factor
+ */
+static void interpolate_mono8_scalar(uint8_t *img_out, const int x, const int y, const int height, const int width,
+						 const uint8_t *img_in, const int coord_x, const int coord_y, const int scale_fact)
+#include "alg_interpolate_mono_scalar.h"
+
+
+/**
+ * Pixel value interpolation of monochrome image (16 bit per pixel).
+ * If a pixel coordinate with a fraction part is of interest, do interpolate the correct value from their neighbor's pixel.
+ * 
+ * E. g. the pixel coordinate x/y = 1.8/2.3 gives the following weights:
+ *          +------+------+
+ *          |      |      |
+ *          | 14%  | 56%  |		14% = 20%*70%, 56% = 80%*70%
+ *          |      |      |
+ *          +------+------+
+ *          |      |      |
+ *          | 6%   | 24%  |		6% = 20%*30%, 24% = 80%*30%
+ *          |      |      |
+ *          +------+------+
+ * 
+ * The weights are applied to the neighors and the resulting pixel value is saved at the given location.
+ * 
+ * NOTE
+ * The input and output image must have the same pixel size.
+ * 
+ * @param img_out On return: image with interpolated values
+ * @param x saved interpolated pixel value at this x-coordinate
+ * @param y saved interpolated pixel value at this y-coordinate
+ * @param height image height of input and output image in number of pixels
+ * @param width image width of input and output image in number of pixels
+ * @param img_in input image to interpolate pixel values
+ * @param coord_x x-coordinate to interpolate
+ * @param coord_y y-coordinate to interpolate
+ * @param scale_fact coordinates are scaled by this factor
+ */
+static void interpolate_mono16_scalar(uint16_t *img_out, const int x, const int y, const int height, const int width,
+						  const uint16_t *img_in, const int coord_x, const int coord_y, const int scale_fact)
+#include "alg_interpolate_mono_scalar.h"
+
+
+/**
+ * Apply iosceles trapez correction.
+ * 
+ * @param data correction data
+ */ 
+static void correct(struct trapcorr_data_t *data) {
+	int x, y, x_corr, y_corr;
+	const int width = data->width;
+	const int height = data->height;
+	int bit_channel =  data->bit_channel;
+	struct coord_t *map = data->map;
+	void *img_calib = data->img_out;
+	void *img_uncalib = data->img_in;
+	const int scale_fact = data->map_scale_fact;
+	const int is_color = data->is_color;
+	
+	
+	for(y = 0; y < height; y++) {
+		for(x = 0; x < width; x++) {
+			x_corr = map->x;
+			y_corr = map->y;
+			map++;
+			
+			if(bit_channel <= 8) {
+				if(is_color) {
+					interpolate_rgb8_scalar(img_calib, x, y, height, width, img_uncalib, x_corr, y_corr, scale_fact);
+				}
+				else {
+					interpolate_mono8_scalar(img_calib, x, y, height, width, img_uncalib, x_corr, y_corr, scale_fact);
+				}
+			}
+			else if(bit_channel <= 16) {
+				if(is_color) {
+					interpolate_rgb16_scalar(img_calib, x, y, height, width, img_uncalib, x_corr, y_corr, scale_fact);
+				}
+				else {
+					interpolate_mono16_scalar(img_calib, x, y, height, width, img_uncalib, x_corr, y_corr, scale_fact);
+				}
+			}
+		}
+	}
+}
+
+
+/**
+ * Initialze perspective correction map.
+ * 
+ * @param data required correction data
+ */ 
+static void init_map(struct trapcorr_data_t *data) {
+	
+	int x, y;
+	struct coord_t *map = data->map;
+	const int scale_fact = (1 << (data->map_scale_fact));
+	const int width = data->width;
+	const int height = data->height;
+	const float p = data->wh * (width/2.0f);
+	float p_i, row_scale, x_corr, y_corr;
+	int x_start, x_end;
+	
+	
+// 	printf("XXX P = %f\n", p);
+	
+	/*
+	 * horizontal correction
+	 */ 
+	if((width%2) == 0) {
+		// even width
+		x_start = (-1)*width/2;
+		x_end = width/2-1;
+	}
+	else {
+		// odd width
+		x_start = (-1)*(width-1)/2;
+		x_end = (width-1)/2;
+	}
+	
+// 	printf("XXX x_start = %d, x_end = %d, %d x %d\n", x_start,  x_end, width, height);
+	
+	for(y = 0; y < height; y++) {
+		
+		p_i = ((width/2.0f - p) / height) * y + p;
+		row_scale = 2.0f * p_i / width;
+		
+		// we don't correct vertically
+		y_corr = y;
+		
+		for(x = x_start; x <= x_end; x++) {
+			x_corr = x/row_scale;
+			
+// 			if(x > -325 && x < -315 && y < 2) {
+// 				printf("%d/%d: p_i = %f, row_scale = %f, x_corr = %f\n", y, x, p_i, row_scale, x_corr);
+// 			}
+			
+			// trapeze is horizontally symmetrically centered --> shift right
+			x_corr -= x_start;
+			
+// 			if(x > -325 && x < -315 && y < 2) {
+// 				printf("    ----> x_corr (shift)= %f\n", x_corr);
+// 			}
+			
+			// range check
+			if(x_corr < 0.0f) {
+				x_corr = 0.0f;
+			}
+			else if(x_corr > (width-1.0f)) {
+				x_corr = width-1.0f;
+			}
+			
+			// apply scaling factor
+			map->x = (int)roundf(x_corr*scale_fact);
+			map->y = (int)roundf(y_corr*scale_fact);
+			map++;
+		}
+	}
+}
+
+
+/**
+ * Apply iosceles trapez correction to given image type.
+ * 
+ * @param trapcorr_data required data for trapez correction
+ * @return 0 on success otherwise -1
+ */
+int trapcorr(struct trapcorr_data_t *trapcorr_data) {
+	
+	/*
+	 * Create perspective correction map if needed.
+	 */ 
+	if(trapcorr_data->map_init == 0) {
+		trapcorr_data->map_scale_fact = 9;	// scale by 9 means 2^9 = 512
+		init_map(trapcorr_data);
+		trapcorr_data->map_init = 1;
+		printf("XXXXX map initialized!\n");
+	}
+	
+	// apply perspective correction
+	correct(trapcorr_data);
+	return 0;
+}