Description
Creates seperate Hue Saturation Value channels from rgb signal.
Introduction
rgb2hsv converts a stream of Red, Green and Blue pixels into their corresponding Hue, Saturation and Value pixels. For more information see the algorithm section.
Features
- 6 clk delay
- Asynchronous reset
- Configurable input wordsize
- fully parameterized testbench
- 3 multipliers (for hue calculation)
Functional description
Algorithm
Hue
The Hue indicates the degrees on the color circle. Starting at 0 degrees with red, 120 degrees for green and 240 degrees for blue. Because 360 degrees does map not correctly on the 8 bits of a byte everything is normalised to the full range of a byte Hue is calculated following the function:
![\[H =\left\{\begin{matrix} 0, & R=G=B\\ \frac{(G-B)*60^{\circ}}{max(R,G,B)-min(R,G,B)}\textup{mod}\:360^{\circ}, & R \geq G,B\\ \frac{(B-R)*60^{\circ}}{max(R,G,B)-min(R,G,B)}+120^{\circ}, & G \geq R,B\\ \frac{(R-G)*60^{\circ}}{max(R,G,B)-min(R,G,B)}+240^{\circ} & B \geq R,G \\ \end{matrix}\right.\]](form_6.png)
Saturation
The saturation indicates the strength of the color. Saturation is calculated following the function:
![\[S =\left\{\begin{matrix} 0, & max(R,G,B)=0 \\ \frac{max(R,G,B)-min(R,G,B)}{max(R,G,B)}, & otherwise\\ \end{matrix}\right.\]](form_7.png)
Value
The value indicates the intensity of the pixel. Value is calculated using the following function:
![\[ V = max(R,G,B)\]](form_8.png)
Rounding issues
TODO calculate the global quantization noise power
Known issues
- Currently limited to use for 8-bit words
- Potentially unneeded multiplier in saturation calculation
Example images
| RGB image | HSV image |
|---|---|
Amersfoort | 
Amersfoort |
Rainbow | 
Rainbow |
Hue gradient | 
Hue gradient |
Saturation gradient | 
Saturation gradient |
Value gradient | 
Value gradient |
Libraries | |
| ieee | |
Use Clauses | |
| std_logic_1164 | |
| numeric_std | |
| math_real | |
| Used for calculation of h_count and v_count port width. | |
Constants | |
| c_60_degrees | integer := integer ( round ( real ( 60 ) / real ( 360 ) * real ( 2 ** wordsize ) ) ) |
| c_120_degrees | integer := integer ( round ( real ( 120 ) / real ( 360 ) * real ( 2 ** wordsize ) ) ) |
| c_240_degrees | integer := integer ( round ( real ( 240 ) / real ( 360 ) * real ( 2 ** wordsize ) ) ) |
Types | |
| mux_select_delay | ( 0 to 4 ) integer range 0 to 2 |
| max_delay | ( 0 to 2 ) integer range 0 to 2 ** wordsize |
Generics | |
| wordsize | integer := 8 |
| input image wordsize in bits | |
Ports | |
| clk | in std_logic |
| completely clocked process | |
| rst | in std_logic |
| asynchronous reset | |
| enable | in std_logic |
| enables block | |
| pixel_red_i | in std_logic_vector ( ( wordsize - 1 ) downto 0 ) |
| red input pixel | |
| pixel_green_i | in std_logic_vector ( ( wordsize - 1 ) downto 0 ) |
| green input pixel | |
| pixel_blue_i | in std_logic_vector ( ( wordsize - 1 ) downto 0 ) |
| blue input pixel | |
| pixel_hue_o | out std_logic_vector ( ( wordsize - 1 ) downto 0 ) |
| hue of pixel | |
| pixel_sat_o | out std_logic_vector ( ( wordsize - 1 ) downto 0 ) |
| saturation of pixel | |
| pixel_val_o | out std_logic_vector ( ( wordsize - 1 ) downto 0 ) |
| value of pixel | |
Member Data Documentation
§ c_120_degrees
|
Constant |
§ c_240_degrees
|
Constant |
§ c_60_degrees
|
Constant |
§ clk
|
Port |
completely clocked process
§ enable
|
Port |
enables block
§ ieee
|
Library |
§ math_real
|
Package |
Used for calculation of h_count and v_count port width.
§ max_delay
§ mux_select_delay
|
Type |
§ numeric_std
|
Package |
§ pixel_blue_i
|
Port |
blue input pixel
§ pixel_green_i
|
Port |
green input pixel
§ pixel_hue_o
|
Port |
hue of pixel
§ pixel_red_i
|
Port |
red input pixel
§ pixel_sat_o
|
Port |
saturation of pixel
§ pixel_val_o
|
Port |
value of pixel
§ rst
|
Port |
asynchronous reset
§ std_logic_1164
|
Package |
§ wordsize
|
Generic |
input image wordsize in bits
The documentation for this class was generated from the following file:
- /home/ben/Programming/VHDL/realtimestagram/src/rgb2hsv/src/rgb2hsv.vhd
