image.c File Reference

Image helper functions, like resizing, color filter, converters... More...

#include "image.h"
#include <stdlib.h>
#include <string.h>

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Functions
void	image_create (struct image_t *img, uint16_t width, uint16_t height, enum image_type type)
	Create a new image. More...
void	image_free (struct image_t *img)
	Free the image. More...
void	image_copy (struct image_t *input, struct image_t *output)
	Copy an image from inut to output This will only work if the formats are the same. More...
void	image_switch (struct image_t *a, struct image_t *b)
	This will switch image *a and *b This is faster as image_copy because it doesn't copy the whole image buffer. More...
void	image_to_grayscale (struct image_t *input, struct image_t *output)
	Convert an image to grayscale. More...
uint16_t	image_yuv422_colorfilt (struct image_t *input, struct image_t *output, uint8_t y_m, uint8_t y_M, uint8_t u_m, uint8_t u_M, uint8_t v_m, uint8_t v_M)
	Filter colors in an YUV422 image. More...
void	image_yuv422_downsample (struct image_t *input, struct image_t *output, uint16_t downsample)
	Simplified high-speed low CPU downsample function without averaging downsample factor must be 1, 2, 4, 8 ... More...
void	image_add_border (struct image_t *input, struct image_t *output, uint8_t border_size)
	This function adds padding to input image by mirroring the edge image elements. More...
void	pyramid_next_level (struct image_t *input, struct image_t *output, uint8_t border_size)
	This function takes previous padded pyramid level and outputs next level of pyramid without padding. More...
void	pyramid_build (struct image_t *input, struct image_t *output_array, uint8_t pyr_level, uint8_t border_size)
	This function populates given array of image_t structs with wanted number of padded pyramids based on given input. More...
void	image_subpixel_window (struct image_t *input, struct image_t *output, struct point_t *center, uint32_t subpixel_factor, uint8_t border_size)
	This outputs a subpixel window image in grayscale Currently only works with Grayscale images as input but could be upgraded to also support YUV422 images. More...
void	image_gradients (struct image_t *input, struct image_t *dx, struct image_t *dy)
	Calculate the gradients using the following matrix: [0 -1 0; -1 0 1; 0 1 0]. More...
void	image_calculate_g (struct image_t *dx, struct image_t *dy, int32_t *g)
	Calculate the G vector of an image gradient This is used for optical flow calculation. More...
uint32_t	image_difference (struct image_t *img_a, struct image_t *img_b, struct image_t *diff)
	Calculate the difference between two images and return the error This will only work with grayscale images. More...
int32_t	image_multiply (struct image_t *img_a, struct image_t *img_b, struct image_t *mult)
	Calculate the multiplication between two images and return the error This will only work with image gradients. More...
void	image_show_points (struct image_t *img, struct point_t *points, uint16_t points_cnt)
	Show points in an image by coloring them through giving the pixels the maximum value. More...
void	image_show_flow (struct image_t *img, struct flow_t *vectors, uint16_t points_cnt, uint8_t subpixel_factor)
	Shows the flow from a specific point to a new point This works on YUV422 and Grayscale images. More...
void	image_draw_line (struct image_t *img, struct point_t *from, struct point_t *to)
	Draw a pink line on the image. More...
void	image_draw_line_color (struct image_t *img, struct point_t *from, struct point_t *to, uint8_t *color)
	Draw a line on the image. More...

Detailed Description

Image helper functions, like resizing, color filter, converters...

Definition in file image.c.

Function Documentation

void image_add_border	(	struct image_t *	input,
		struct image_t *	output,
		uint8_t	border_size
	)

This function adds padding to input image by mirroring the edge image elements.

Parameters

[in]	*input	- input image (grayscale only)
[out]	*output	- the output image
[in]	border_size	- amount of padding around image. Padding is made by reflecting image elements at the edge Example: f e d c b a | a b c d e f | f e d c b a

Definition at line 245 of file image.c.

References image_t::buf, image_t::h, image_create(), image_t::type, and image_t::w.

Referenced by pyramid_build().

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void image_calculate_g	(	struct image_t *	dx,
		struct image_t *	dy,
		int32_t *	g
	)

Calculate the G vector of an image gradient This is used for optical flow calculation.

Parameters

[in]	*dx	The gradient in the X direction
[in]	*dy	The gradient in the Y direction
[out]	*g	The G[4] vector devided by 255 to keep in range

Definition at line 446 of file image.c.

References image_t::buf, image_t::h, and image_t::w.

Referenced by opticFlowLK(), and opticFlowLK_flat().

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void image_copy	(	struct image_t *	input,
		struct image_t *	output
	)

Copy an image from inut to output This will only work if the formats are the same.

Parameters

[in]	*input	The input image to copy from
[out]	*output	The out image to copy to

Definition at line 77 of file image.c.

References image_t::buf, image_t::buf_size, image_t::h, image_t::ts, image_t::type, and image_t::w.

Referenced by calc_fast9_lukas_kanade(), and cv_async_function().

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void image_create	(	struct image_t *	img,
		uint16_t	width,
		uint16_t	height,
		enum image_type	type
	)

Create a new image.

Parameters

[out]	*img	The output image
[in]	width	The width of the image
[in]	height	The height of the image
[in]	type	The type of image (YUV422 or grayscale)

Definition at line 38 of file image.c.

References image_t::buf, image_t::buf_size, image_t::h, IMAGE_GRADIENT, IMAGE_JPEG, IMAGE_YUV422, image_t::type, and image_t::w.

Referenced by calc_fast9_lukas_kanade(), cv_async_function(), cv_blob_locator_func(), cv_window_func(), detect_window(), image_add_border(), log_image(), opticFlowLK(), opticFlowLK_flat(), pyramid_next_level(), qrscan(), video_capture_save(), video_thread_function(), and viewvideo_function().

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uint32_t image_difference	(	struct image_t *	img_a,
		struct image_t *	img_b,
		struct image_t *	diff
	)

Calculate the difference between two images and return the error This will only work with grayscale images.

Parameters

[in]	*img_a	The image to substract from
[in]	*img_b	The image to substract from img_a
[out]	*diff	The image difference (if not needed can be NULL)

Returns

The squared difference summed

Definition at line 478 of file image.c.

References image_t::buf, image_t::h, and image_t::w.

Referenced by opticFlowLK(), and opticFlowLK_flat().

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void image_draw_line	(	struct image_t *	img,
		struct point_t *	from,
		struct point_t *	to
	)

Draw a pink line on the image.

Parameters

[in,out]	*img	The image to show the line on
[in]	*from	The point to draw from
[in]	*to	The point to draw to

Definition at line 600 of file image.c.

References image_draw_line_color().

Referenced by draw_edgeflow_img(), image_show_flow(), and qrscan().

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void image_draw_line_color	(	struct image_t *	img,
		struct point_t *	from,
		struct point_t *	to,
		uint8_t *	color
	)

Draw a line on the image.

Parameters

[in,out]	*img	The image to show the line on
[in]	*from	The point to draw from
[in]	*to	The point to draw to
[in]	*color	The line color as a [U, Y1, V, Y2] uint8_t array, or a uint8_t value pointer for grayscale images. Example colors: white = {127, 255, 127, 255}, green = {0, 127, 0, 127};

Definition at line 613 of file image.c.

References image_t::buf, image_t::h, IMAGE_YUV422, image_t::type, image_t::w, point_t::x, and point_t::y.

Referenced by image_draw_line().

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void image_free

(

struct image_t *

img

)

Free the image.

Parameters

[in]

*img

The image to free

Definition at line 63 of file image.c.

References image_t::buf.

Referenced by cv_blob_locator_func(), cv_window_func(), detect_window(), opticFlowLK(), opticFlowLK_flat(), pyramid_build(), video_capture_save(), video_thread_function(), and viewvideo_function().

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void image_gradients	(	struct image_t *	input,
		struct image_t *	dx,
		struct image_t *	dy
	)

Calculate the gradients using the following matrix: [0 -1 0; -1 0 1; 0 1 0].

Parameters

[in]	*input	Input grayscale image
[out]	*dx	Output gradient in the X direction (dx->w = input->w-2, dx->h = input->h-2)
[out]	*dy	Output gradient in the Y direction (dx->w = input->w-2, dx->h = input->h-2)

Definition at line 422 of file image.c.

References image_t::buf, image_t::h, and image_t::w.

Referenced by opticFlowLK(), and opticFlowLK_flat().

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int32_t image_multiply	(	struct image_t *	img_a,
		struct image_t *	img_b,
		struct image_t *	mult
	)

Calculate the multiplication between two images and return the error This will only work with image gradients.

Parameters

[in]	*img_a	The image to multiply
[in]	*img_b	The image to multiply with
[out]	*mult	The image multiplication (if not needed can be NULL)

Returns

The sum of the multiplcation

Definition at line 516 of file image.c.

References image_t::buf, image_t::h, and image_t::w.

Referenced by opticFlowLK(), and opticFlowLK_flat().

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void image_show_flow	(	struct image_t *	img,
		struct flow_t *	vectors,
		uint16_t	points_cnt,
		uint8_t	subpixel_factor
	)

Shows the flow from a specific point to a new point This works on YUV422 and Grayscale images.

Parameters

[in,out]	*img	The image to show the flow on
[in]	*vectors	The flow vectors to show
[in]	*points_cnt	The amount of points and vectors to show

Definition at line 577 of file image.c.

References flow_t::flow_x, flow_t::flow_y, image_draw_line(), flow_t::pos, point_t::x, and point_t::y.

Referenced by calc_fast9_lukas_kanade().

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void image_show_points	(	struct image_t *	img,
		struct point_t *	points,
		uint16_t	points_cnt
	)

Show points in an image by coloring them through giving the pixels the maximum value.

This works with YUV422 and grayscale images

Parameters

[in,out]	*img	The image to place the points on
[in]	*points	The points to sohw
[in]	*points_cnt	The amount of points to show

Definition at line 552 of file image.c.

References image_t::buf, idx, IMAGE_YUV422, image_t::type, image_t::w, point_t::x, and point_t::y.

Referenced by calc_fast9_lukas_kanade().

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void image_subpixel_window	(	struct image_t *	input,
		struct image_t *	output,
		struct point_t *	center,
		uint32_t	subpixel_factor,
		uint8_t	border_size
	)

This outputs a subpixel window image in grayscale Currently only works with Grayscale images as input but could be upgraded to also support YUV422 images.

You can and should only ask a subpixel window of a center point that is w/2 pixels away from the edges

Parameters

[in]	*input	Input image (grayscale only)
[out]	*output	Window output (width and height is used to calculate the window size)
[in]	*center	Center point in subpixel coordinates
[in]	subpixel_factor	The subpixel factor per pixel
[in]	border_size	- amount of padding around image. Padding is made by reflecting image elements at the edge Example: f e d c b a | a b c d e f | f e d c b a

Definition at line 364 of file image.c.

References image_t::buf, image_t::h, image_t::w, point_t::x, and point_t::y.

Referenced by opticFlowLK(), and opticFlowLK_flat().

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void image_switch	(	struct image_t *	a,
		struct image_t *	b
	)

This will switch image *a and *b This is faster as image_copy because it doesn't copy the whole image buffer.

Parameters

[in,out]	*a	The image to switch
[in,out]	*b	The image to switch with

Definition at line 97 of file image.c.

Referenced by calc_fast9_lukas_kanade().

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void image_to_grayscale	(	struct image_t *	input,
		struct image_t *	output
	)

Convert an image to grayscale.

Depending on the output type the U/V bytes are removed

Parameters

[in]	*input	The input image (Needs to be YUV422)
[out]	*output	The output image

Definition at line 116 of file image.c.

References image_t::buf, dest, image_t::h, IMAGE_YUV422, image_t::ts, image_t::type, and image_t::w.

Referenced by calc_fast9_lukas_kanade(), cv_window_func(), and detect_window().

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uint16_t image_yuv422_colorfilt	(	struct image_t *	input,
		struct image_t *	output,
		uint8_t	y_m,
		uint8_t	y_M,
		uint8_t	u_m,
		uint8_t	u_M,
		uint8_t	v_m,
		uint8_t	v_M
	)

Filter colors in an YUV422 image.

Parameters

[in]	*input	The input image to filter
[out]	*output	The filtered output image
[in]	y_m	The Y minimum value
[in]	y_M	The Y maximum value
[in]	u_m	The U minimum value
[in]	u_M	The U maximum value
[in]	v_m	The V minimum value
[in]	v_M	The V maximum value

Returns

The amount of filtered pixels

Definition at line 149 of file image.c.

References image_t::buf, dest, image_t::h, image_t::ts, and image_t::w.

Referenced by colorfilter_func().

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void image_yuv422_downsample	(	struct image_t *	input,
		struct image_t *	output,
		uint16_t	downsample
	)

Simplified high-speed low CPU downsample function without averaging downsample factor must be 1, 2, 4, 8 ...

2^X image of type UYVY expected. Only one color UV per 2 pixels

we keep the UV color of the first pixel pair and sample the intensity evenly 1-3-5-7-... or 1-5-9-...

input: u1y1 v1y2 u3y3 v3y4 u5y5 v5y6 u7y7 v7y8 ... downsample=1 u1y1 v1y2 u3y3 v3y4 u5y5 v5y6 u7y7 v7y8 ... downsample=2 u1y1v1 (skip2) y3 (skip2) u5y5v5 (skip2) y7 (skip2) ... downsample=4 u1y1v1 (skip6) y5 (skip6) ...

Parameters

[in]	*input	The input YUV422 image
[out]	*output	The downscaled YUV422 image
[in]	downsample	The downsample factor (must be downsample=2^X)

Definition at line 213 of file image.c.

References image_t::buf, dest, image_t::h, image_t::ts, and image_t::w.

Referenced by viewvideo_function().

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void pyramid_build	(	struct image_t *	input,
		struct image_t *	output_array,
		uint8_t	pyr_level,
		uint8_t	border_size
	)

This function populates given array of image_t structs with wanted number of padded pyramids based on given input.

Parameters

[in]	*input	- input image (grayscale only)
[out]	*output	- array of image_t structs containing image pyiramid levels. Level zero contains original image, followed by pyr_level of pyramid.
[in]	pyr_level	- number of pyramids to be built. If 0, original image is padded and outputed.
[in]	border_size	- amount of padding around image. Padding is made by reflecting image elements at the edge Example: f e d c b a | a b c d e f | f e d c b a

Definition at line 337 of file image.c.

References image_add_border(), image_free(), and pyramid_next_level().

Referenced by opticFlowLK().

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void pyramid_next_level	(	struct image_t *	input,
		struct image_t *	output,
		uint8_t	border_size
	)

This function takes previous padded pyramid level and outputs next level of pyramid without padding.

For calculating new pixel value 5x5 filter matrix suggested by Bouguet is used: [1/16 1/8 3/4 1/8 1/16]' x [1/16 1/8 3/4 1/8 1/16] To avoid decimal numbers, all coefficients are multiplied by 10000.

Parameters

[in]	*input	- input image (grayscale only)
[out]	*output	- the output image
[in]	border_size	- amount of padding around image. Padding is made by reflecting image elements at the edge Example: f e d c b a | a b c d e f | f e d c b a

Definition at line 290 of file image.c.

References image_t::buf, image_t::h, image_create(), image_t::type, and image_t::w.

Referenced by pyramid_build().

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