MareArts Computer Vision Study.: 2012.11

11/06/2012

YUV color format (444, 422, 411) - simple explanation

In the YUV color format, Y is bright information, U is blue color area, V is red color area.
Show the below picture. The picture is u-v color map

There are 3 type color format of YUV.

The types are 444, 422, 411.

444 is one pixel is 24 bits.

422 is one pixel is 16 bits.

And U0, V0 is shared by Y0, Y1.

411 is one pixel is 12 bits.

This source code is convert code from YUV422 to RGB.

/ 


void ConvertYUV422toRGB(unsigned char** pSrc, unsigned char** pDst,int width,int height){
int i,j;
unsigned char* dst=*pDst;
unsigned char* src=*pSrc;
int Y1,Y2,U,V;
int R,G,B;

for(i=0;i2)
{
Y1=src[i*2+1];
Y2=src[i*2+3];
U=src[i*2];
V=src[i*2+2];

dst[i*3+2]=(unsigned char)((float)Y1+(1.4075f*(float)(V-128)));
dst[i*3+1]=(unsigned char)((float)Y1+(0.3455f*(float)(U-128)-(0.7169f*(float)(V-128))));
dst[i*3]=(unsigned char)((float)Y1+(1.7790f*(float)(U-128)));
dst[i*3+5]=(unsigned char)((float)Y2+(1.4075f*(float)(V-128)));
dst[i*3+4]=(unsigned char)((float)Y2+(0.3455f*(float)(U-128)-(0.7169f*(float)(V-128))));
dst[i*3+3]=(unsigned char)((float)Y2+(1.7790f*(float)(U-128)));
}
}

And YUV is converted by below fomulation.

R = Y + 1.4075(V-128)
G = Y - 0.3455(U-128) - 0.7169(V-128)
B = Y + 1.7790(U-128)

Thanks you.

sorry last source code is broken.
becasue html tag..
So I upload new version convert source code.
note!!! check Y position, the position is different as machine environment..
In the source code, stride means real width size.
YUV422 to RGB
--

//yuv to rgb
 int Y,U,V;   
 int R1,G1,B1;
 for(int ih=0; ihm_height; ++ih)
 {   
  //int iww=0;
  for(int iw=0; iwm_width; iw++)
  {
  
   if(iw %2 == 0)
   {
    Y = obj->m_yuv[ih*obj->m_stride + iw*2 + 0];
    U = obj->m_yuv[ih*obj->m_stride + iw*2 + 1];
    V = obj->m_yuv[ih*obj->m_stride + iw*2 + 3];
   }else{
    Y = obj->m_yuv[ih*obj->m_stride + iw*2 + 0];
    U = obj->m_yuv[ih*obj->m_stride + iw*2 -1];
    V = obj->m_yuv[ih*obj->m_stride + iw*2 + 1];
   }
   
   R1 = Y + 1.4075*(V-128);
   G1 = Y - 0.3455*(U-128) - 0.7169*(V-128);
   B1 = Y + 1.7790*(U-128);

   o_Image2.at(ih, iw)[0] = BYTE(MMIN(255, MMAX(0, B1)));// B1;
   o_Image2.at(ih, iw)[1] = BYTE(MMIN(255, MMAX(0, G1)));// G1;
   o_Image2.at(ih, iw)[2] = BYTE(MMIN(255, MMAX(0, R1)));// R1;
  }
 }

--
RGB to YUV422
--

int Y,U,V;   
   int R1,G1,B1;
   for(int ih=0; ih< obj->m_height; ++ih)
   {   
    //int iww=0;
    for(int iw=0; iw< obj->m_width; iw++)
    {

     B1 = o_Image2.at< cv::Vec3b>(ih, iw)[0];// B1;
     G1 = o_Image2.at< cv::Vec3b>(ih, iw)[1];// G1;
     R1 = o_Image2.at< cv::Vec3b>(ih, iw)[2];// R1;

     Y = (0.257*R1) + (0.504*G1) + (0.098*B1) +16;
     U = -(0.148*R1) - (0.291*G1) + (0.439*B1) + 128;
     V = (0.439*R1 ) - (0.368*G1) - (0.071*B1) + 128;
     Y = MMIN(255, MMAX(0, Y));
     U = MMIN(255, MMAX(0, U));
     V = MMIN(255, MMAX(0, V));

     if(iw %2 == 0)
     {
      obj->m_yuv[ih*obj->m_stride + iw*2 + 0] = Y;
      obj->m_yuv[ih*obj->m_stride + iw*2 + 1] = U;
      obj->m_yuv[ih*obj->m_stride + iw*2 + 3] = V;
     }else{
      obj->m_yuv[ih*obj->m_stride + iw*2 + 0] = Y;
      obj->m_yuv[ih*obj->m_stride + iw*2 -1] = U;
      obj->m_yuv[ih*obj->m_stride + iw*2 + 1] = V;
     }     
    }

11/01/2012

clapack example source and method to use

clapack is math library to solve linear algebra in C language.
Originally, it is library to use in fortran language.
but clapack is made to use in C language.

1. You can see the method to use and file download on this site(http://icl.cs.utk.edu/lapack-for-windows/index.html)

Or

2. You can download pre-bulit clapack lib in here. I am using this lib now.
It might not run well, if the environment of your computer was different with me.
My environment is window 7 32bit, vs 2008.
The method to use is easy.
- Copy lib, header files in your project (The compressed file includes 'blas.lib, blasd.lib, lapack.lib, lapackd.lib, libf2c.lib, libf2cd.lib, clapack.h, f2c.h'.)
- Set Additional Dependencies on project property.
Add these libs "blas.lib lapack.lib libf2c.lib"
- include this header file on your source code.
#include "f2c.h"
#include "clapack.h"
- use functions of lapack.

this is example source code.

/*
    DGESV Example.
    ==============
  
    The program computes the solution to the system of linear
    equations with a square matrix A and multiple
    right-hand sides B, where A is the coefficient matrix:
  
      6.80  -6.05  -0.45   8.32  -9.67
     -2.11  -3.30   2.58   2.71  -5.14
      5.66   5.36  -2.70   4.35  -7.26
      5.97  -4.44   0.27  -7.17   6.08
      8.23   1.08   9.04   2.14  -6.87
 
   and B is the right-hand side matrix:
  
      4.02  -1.56   9.81
      6.19   4.00  -4.09
     -8.22  -8.67  -4.57
     -7.57   1.75  -8.61
     -3.03   2.86   8.99
  
    Description.
    ============
  
    The routine solves for X the system of linear equations A*X = B,
    where A is an n-by-n matrix, the columns of matrix B are individual
    right-hand sides, and the columns of X are the corresponding
    solutions.
 
   The LU decomposition with partial pivoting and row interchanges is
    used to factor A as A = P*L*U, where P is a permutation matrix, L
    is unit lower triangular, and U is upper triangular. The factored
    form of A is then used to solve the system of equations A*X = B.
 
   Example Program Results.
    ========================
  
  DGESV Example Program Results
 
 Solution
   -0.80  -0.39   0.96
   -0.70  -0.55   0.22
    0.59   0.84   1.90
    1.32  -0.10   5.36
    0.57   0.11   4.04
 
 Details of LU factorization
    8.23   1.08   9.04   2.14  -6.87
    0.83  -6.94  -7.92   6.55  -3.99
    0.69  -0.67 -14.18   7.24  -5.19
    0.73   0.75   0.02 -13.82  14.19
   -0.26   0.44  -0.59  -0.34  -3.43
 
 Pivot indices
       5      5      3      4      5
 */

#include 
#include 

#include "f2c.h"
#include "clapack.h"


 extern void print_matrix( char* desc, int m, int n, double* a, int lda );
 extern void print_int_vector( char* desc, int n, int* a );
 
/* Parameters */
 #define N 5
 #define NRHS 3
 #define LDA N
 #define LDB N
 
/* Main program */
 int main() {
         /* Locals */
         integer n = N, nrhs = NRHS, lda = LDA, ldb = LDB, info;
         /* Local arrays */
         integer ipiv[N];
         double a[LDA*N] = {
             6.80, -2.11,  5.66,  5.97,  8.23,
            -6.05, -3.30,  5.36, -4.44,  1.08,
            -0.45,  2.58, -2.70,  0.27,  9.04,
             8.32,  2.71,  4.35, -7.17,  2.14,
            -9.67, -5.14, -7.26,  6.08, -6.87
         };
         double b[LDB*NRHS] = {
             4.02,  6.19, -8.22, -7.57, -3.03,
            -1.56,  4.00, -8.67,  1.75,  2.86,
             9.81, -4.09, -4.57, -8.61,  8.99
         };
         /* Executable statements */
         printf( " DGESV Example Program Results\n" );
         /* Solve the equations A*X = B */
         dgesv_( &n, &nrhs, a, &lda, ipiv, b, &ldb, &info );
         /* Check for the exact singularity */
         if( info > 0 ) {
                 printf( "The diagonal element of the triangular factor of A,\n" );
                 printf( "U(%i,%i) is zero, so that A is singular;\n", info, info );
                 printf( "the solution could not be computed.\n" );
                 exit( 1 );
         }
         /* Print solution */
         print_matrix( "Solution", n, nrhs, b, ldb );
         /* Print details of LU factorization */
         print_matrix( "Details of LU factorization", n, n, a, lda );
         /* Print pivot indices */
         print_int_vector( "Pivot indices", n, (int*)ipiv );
         exit( 0 );
 } /* End of DGESV Example */
 
/* Auxiliary routine: printing a matrix */
 void print_matrix( char* desc, int m, int n, double* a, int lda ) {
         int i, j;
         printf( "\n %s\n", desc );
         for( i = 0; i < m; i++ ) {
                 for( j = 0; j < n; j++ ) printf( " %6.2f", a[i+j*lda] );
                 printf( "\n" );
         }
 }
 
/* Auxiliary routine: printing a vector of integers */
 void print_int_vector( char* desc, int n, int* a ) {
         int j;
         printf( "\n %s\n", desc );
         for( j = 0; j < n; j++ ) printf( " %6i", a[j] );
         printf( "\n" );


 }