Image Format Conversion: RGB to YUV

This example shows how to generate HDL code from a MATLAB® design implementing a RGB2YUV conversion.

MATLAB Design

design_name = 'mlhdlc_rgb2yuv';
testbench_name = 'mlhdlc_rgb2yuv_tb';

Let us take a look at the MATLAB design

type(design_name);

function [x_out, y_out, y_data_out, u_data_out, v_data_out] = mlhdlc_rgb2yuv(x_in, y_in, r_in, g_in, b_in)
%#codegen

%   Copyright 2011-2015 The MathWorks, Inc.

persistent RGB_Reg YUV_Reg
persistent x1 x2 y1 y2

if isempty(RGB_Reg)
    RGB_Reg = zeros(3,1);
    YUV_Reg = zeros(3,1);
    x1 = 0;
    x2 = 0;
    y1 = 0;
    y2 = 0;
end

D = [.299  .587  .144; 
    -.147 -.289  .436; 
     .615 -.515 -.1];
C = [0; 128; 128];

RGB = [r_in; g_in; b_in];

YUV_1 = D*RGB_Reg;
YUV_2 = YUV_1 + C;
RGB_Reg = RGB;

y_data_out = round(YUV_Reg(1));
u_data_out = round(YUV_Reg(2));
v_data_out = round(YUV_Reg(3));
YUV_Reg = YUV_2;

x_out = x2;
x2 = x1;
x1 = x_in;
y_out = y2;
y2 = y1;
y1 = y_in;

type(testbench_name);


%   Copyright 2011-2015 The MathWorks, Inc.

FRAMES = 1;
WIDTH = 752;
HEIGHT = 480;
HBLANK = 10;%748;
VBLANK = 10;%120;

vidData = double(imread('mlhdlc_img_yuv.tif'));


for f = 1:FRAMES
    vidOut = zeros(HEIGHT, WIDTH, 3);
    
    for y = 0:HEIGHT+VBLANK-1
        for x = 0:WIDTH+HBLANK-1
            if y >= 0 && y < HEIGHT && x >= 0 && x < WIDTH
                b = vidData(y+1,x+1,1);
                g = vidData(y+1,x+1,2);
                r = vidData(y+1,x+1,3);
            else
                b = 0;
                g = 0;
                r = 0;
            end           

            [xOut, yOut, yData, uData, vData] = ...
                mlhdlc_rgb2yuv(x, y, r, g, b);

            if yOut >= 0 && yOut < HEIGHT && xOut >= 0 && xOut < WIDTH
                vidOut(yOut+1,xOut+1,:) = [yData vData uData];
            end     
        end  
    end
    
    figure(1);
    subplot(1,2,1); 
    imshow(uint8(vidData));
    subplot(1,2,2); 
    imshow(ycbcr2rgb(uint8(vidOut)));
    drawnow;            
            
end

Setup for the Example

Executing the following lines of code copies the necessary example files into a temporary folder

mlhdlc_demo_dir = fullfile(matlabroot, 'toolbox', 'hdlcoder', 'hdlcoderdemos', 'matlabhdlcoderdemos');
mlhdlc_temp_dir = [tempdir 'mlhdlc_rgb2yuv'];

% create a temporary folder and copy the MATLAB files
cd(tempdir);
[~, ~, ~] = rmdir(mlhdlc_temp_dir, 's');
mkdir(mlhdlc_temp_dir);
cd(mlhdlc_temp_dir);

% copy files to the temp dir
copyfile(fullfile(mlhdlc_demo_dir, [design_name,'.m*']), mlhdlc_temp_dir);
copyfile(fullfile(mlhdlc_demo_dir, [testbench_name,'.m*']), mlhdlc_temp_dir);

Simulate the Design

It is always a good practice to simulate the design with the testbench prior to code generation to make sure there are no runtime errors.

mlhdlc_rgb2yuv_tb

Create a New HDL Coder™ Project

  coder -hdlcoder -new mlhdlc_rgb_prj

Next, add the file 'mlhdlc_rgb2yuv.m' to the project as the MATLAB Function and 'mlhdlc_rgb2yuv_tb.m' as the MATLAB Test Bench.

You can refer to Getting Started with MATLAB to HDL Workflow tutorial for a more complete tutorial on creating and populating MATLAB HDL Coder projects.

Run Fixed-Point Conversion and HDL Code Generation

Launch HDL Advisor and right click on the 'Code Generation' step and choose the option 'Run to selected task' to run all the steps from the beginning through the HDL code generation.

Examine the generated HDL code by clicking on the hyperlinks in the Code Generation Log window.

Clean up the Generated Files

You can run the following commands to clean up the temporary project folder.

mlhdlc_demo_dir = fullfile(matlabroot, 'toolbox', 'hdlcoder', 'hdlcoderdemos', 'matlabhdlcoderdemos');
mlhdlc_temp_dir = [tempdir 'mlhdlc_rgb2yuv'];
clear mex;
cd (mlhdlc_demo_dir);
rmdir(mlhdlc_temp_dir, 's');

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