need help with mean and standard deviation

[FORTRANS]

hi Steve
well - the 4shared page has about 20 download buttons on it - lol
and when you find the right one - you have to sign in to get it

Hi Dave,

   Right.  That explains what happened, except for the EXE
download.  Thanks.

maybe Christian Graus can help with the colors...
this is part 6 of a 6-part series
http://www.codeproject.com/Articles/7138/Image-Processing-for-Dummies-with-C-and-GDI-Part-6

   That looks okay to explain the HLS color space.  Lab is a
bit different.

What i´m trying to understand and create is the formulas described in the chapter

3. AUTOMATIC SELECTIVE COLOR TRANSFER ALGORITHM FOR IMAGES
3.1 New mean and standard deviation values of ASCT algorithm

page 2 of the pdf i uploaded

I don´t know what they means so i can try to code them.

   He is applying image processing to images based on the
the statistics (mean, standard deviation) of portions of the
images.  He can adjust the processing so it applies to image
regions that appear rather different.  The book I have uses
something similar to sharpen images.  Using the average
pixel values of a small region to lighten dark areas for instance.
And using differing amounts of sharpening based on the local
standard deviation of the pixels.

Regards,

Steve

[dedndave]

the EXE is probably an "ilivid" downloader, custom to that specific file
i think they're safe - but i still prefer not to download and run EXE's like that   :redface:

[guga]

livid ? dont dl it !. 4shared have some merchandising...Only dl the rar file after the circle is runnin when you press to dl

[dedndave]

i have tried ilivid in the past
as i recall, it was pretty easy to remove any ad-ware remnants after you get what you want

[guga]

dave, i´m trying to convert this to C so it can be easy to analyse, but VisualStudio 10 is refusing to compiler....What i´m making wrong here ?

I´m trying to convert it to plain C (No c++), but VS keeps giving me errors

Original code

Code Select Expand


vec3 RGB2Lab(in vec3 rgb){
    float R = rgb.x;
    float G = rgb.y;
    float B = rgb.z;
    // threshold
    float T = 0.008856;

    float X = R * 0.412453 + G * 0.357580 + B * 0.180423;
    float Y = R * 0.212671 + G * 0.715160 + B * 0.072169;
    float Z = R * 0.019334 + G * 0.119193 + B * 0.950227;

    // Normalize for D65 white point
    X = X / 0.950456;
    Y = Y;
    Z = Z / 1.088754;

    bool XT, YT, ZT;
    XT = false; YT=false; ZT=false;
    if(X > T) XT = true;
    if(Y > T) YT = true;
    if(Z > T) ZT = true;

    float Y3 = pow(Y,1/3f);
    float fX, fY, fZ;
    if(XT){ fX = pow(X, 1/3f);} else{ fX = 7.787 * X + 16/116; }
    if(YT){ fY = Y3; } else{ fY = 7.787 * Y + 16/116 ; }
    if(ZT){ fZ = pow(Z,1/3f); } else{ fZ = 7.787 * Z + 16/116; }

    float L; if(YT){ L = (116 * Y3) - 16.0; }else { L = 903.3 * Y; }
    float a = 500 * ( fX - fY );
    float b = 200 * ( fY - fZ );

    return vec3(L,a,b);
}


Code Select Expand


vec3 Lab2RGB(in vec3 lab){
    //Thresholds
    float T1 = 0.008856;
    float T2 = 0.206893;

    float X,Y,Z;

    //Compute Y
    bool XT, YT, ZT;
    XT = false; YT=false; ZT=false;

    float fY = pow(((lab.x + 16.0) / 116.0),3);
    if(fY > T1){ YT = true; }
    if(YT){ fY = fY; } else{ fY = (lab.x / 903.3); }
    Y = fY;

    //Alter fY slightly for further calculations
    if(YT){ fY = pow(fY,1/3f); } else{ fY = (7.787 * fY + 16.0/116.0); }

    //Compute X
    float fX = ( lab.y / 500.0 ) + fY;
    if(fX > T2){ XT = true; }
    if(XT){ X = pow(fX,3); } else{X = ((fX - (16/116.0)) / 7.787); }

    //Compute Z
    float fZ = fY - ( lab.z / 200.0 );
    if(fZ > T2){ ZT = true; }
    if(ZT){ Z = pow(fZ,3); } else{ Z = ((fZ - (16/116.0)) / 7.787); }

    //Normalize for D65 white point
    X = X * 0.950456;
    Z = Z * 1.088754;

    //XYZ to RGB part
    float R =  3.240479 * X + -1.537150 * Y + -0.498535 * Z;
    float G = -0.969256 * X +  1.875991 * Y +  0.041556 * Z;
    float B =  0.055648 * X + -0.204043 * Y +  1.057311 * Z;

    return vec3(R,G,B);
}



Mine code:

Code Select Expand


struct lab{
  float x;
  float y;
  float z;
} lab; // this is just a random name not mine!

void Lab2RGB(struct lab *lab){
    //Thresholds
    float T1 = 0.008856;
    float T2 = 0.206893;

    float X,Y,Z;

    //Compute Y
    bool XT, YT, ZT;
    XT = false; YT=false; ZT=false;

    float fY = pow(((lab.x + 16.0) / 116.0),3);
    if(fY > T1){ YT = true; }
    if(YT){ fY = fY; } else{ fY = (lab.x / 903.3); }
    Y = fY;

    //Alter fY slightly for further calculations
    if(YT){ fY = pow(fY,1/3f); } else{ fY = (7.787 * fY + 16.0/116.0); }

    //Compute X
    float fX = ( lab.y / 500.0 ) + fY;
    if(fX > T2){ XT = true; }
    if(XT){ X = pow(fX,3); } else{X = ((fX - (16/116.0)) / 7.787); }

    //Compute Z
    float fZ = fY - ( lab.z / 200.0 );
    if(fZ > T2){ ZT = true; }
    if(ZT){ Z = pow(fZ,3); } else{ Z = ((fZ - (16/116.0)) / 7.787); }

    //Normalize for D65 white point
    X = X * 0.950456;
    Z = Z * 1.088754;

    //XYZ to RGB part
    float R =  3.240479 * X + -1.537150 * Y + -0.498535 * Z;
    float G = -0.969256 * X +  1.875991 * Y +  0.041556 * Z;
    float B =  0.055648 * X + -0.204043 * Y +  1.057311 * Z;

    //return vec3(R,G,B); ????????????? how to return it properly ?
}



The reason is that i suceeded (i guess) to port the RGB2Lab, but when i did the opposite function (LAb2RGB) the image turns onto Green !

Can someone port this functions to VS or masm, so i can analyse them to see how they works ?

[TWell]

try this:

Code Select Expand

// TestRGB2Lab.c for msvc
#include <stdio.h>
//#include <stdbool.h>
#include <math.h>

typedef int bool;
#define true 1
#define false 0

typedef struct _VEC3
{
float x,y,z;
} VEC3, *PVEC3;

VEC3 RGB2Lab(VEC3 rgb)
{
VEC3 rv3;
float R = rgb.x;
float G = rgb.y;
float B = rgb.z;
// threshold
float T = 0.008856;

float X = R * 0.412453 + G * 0.357580 + B * 0.180423;
float Y = R * 0.212671 + G * 0.715160 + B * 0.072169;
float Z = R * 0.019334 + G * 0.119193 + B * 0.950227;
bool XT, YT, ZT;
float fX, fY, fZ;
float Y3;
float L;
float a, b;

// Normalize for D65 white point
X = X / 0.950456;
//Y = Y;
Z = Z / 1.088754;

if (X > T) XT = true; else XT = false;
if (Y > T) YT = true; else YT = false;
if (Z > T) ZT = true; else ZT = false;

Y3 = pow(Y, 1 / 3.0);
if (XT) {
fX = pow(X, 1 / 3.0);
} else {
fX = 7.787 * X + 16 / 116;
}
if (YT) {
fY = Y3;
} else {
fY = 7.787 * Y + 16 / 116;
}
if (ZT) {
fZ = pow(Z, 1 / 3.0);
} else {
fZ = 7.787 * Z + 16 / 116;
}

if (YT) {
L = (116 * Y3) - 16.0;
} else {
L = 903.3 * Y;
}
a = 500 * (fX - fY);
b = 200 * (fY - fZ);

//return vec3(L, a, b);
rv3.x = L;
rv3.y = a;
rv3.z = b;
return rv3;
}

VEC3 Lab2RGB(VEC3 lab)
{
VEC3 rv3;
//Thresholds
float T1 = 0.008856;
float T2 = 0.206893;

float X, Y, Z;
float fX, fY, fZ;
float R, G, B;

//Compute Y
bool XT, YT, ZT;
XT = false;
YT = false;
ZT = false;

fY = pow(((lab.x + 16.0) / 116.0), 3);
if (fY > T1) {
YT = true;
}
if (YT) {
fY = fY;
} else {
fY = (lab.x / 903.3);
}
Y = fY;

//Alter fY slightly for further calculations
if (YT) {
fY = pow(fY, 1 / 3.0);
} else {
fY = (7.787 * fY + 16.0 / 116.0);
}

//Compute X
fX = (lab.y / 500.0) + fY;
if (fX > T2) {
XT = true;
}
if (XT) {
X = pow(fX, 3);
} else {
X = ((fX - (16 / 116.0)) / 7.787);
}

//Compute Z
fZ = fY - (lab.z / 200.0);
if (fZ > T2) {
ZT = true;
}
if (ZT) {
Z = pow(fZ, 3);
} else {
Z = ((fZ - (16 / 116.0)) / 7.787);
}

//Normalize for D65 white point
X = X * 0.950456;
Z = Z * 1.088754;

//XYZ to RGB part
R = 3.240479 * X + -1.537150 * Y + -0.498535 * Z;
G = -0.969256 * X + 1.875991 * Y + 0.041556 * Z;
B = 0.055648 * X + -0.204043 * Y + 1.057311 * Z;

rv3.x = R;
rv3.y = G;
rv3.z = B;
return rv3;
//return vec3(R, G, B);
}

int main(int argc, char **argv)
{
VEC3 v3;
v3.x = 50.0;
v3.y = 50.0;
v3.z = 50.0;
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
v3 = Lab2RGB(v3); // pass copy of v3
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
v3 = RGB2Lab(v3); // pass copy of v3
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
return 0;
}Can anyone try this version with MSVS 2013 in C mode (C99)?
With PellesC one can compile it.

Code Select Expand

// RGB2LabTest.c for C99
#include <stdio.h>
#include <stdbool.h>
#include <math.h>

typedef struct _VEC3
{
float x,y,z;
} VEC3, *pvec3;

VEC3 RGB2Lab(VEC3 rgb)
{
VEC3 rv3;
float R = rgb.x;
float G = rgb.y;
float B = rgb.z;
// threshold
float T = 0.008856;

float X = R * 0.412453 + G * 0.357580 + B * 0.180423;
float Y = R * 0.212671 + G * 0.715160 + B * 0.072169;
float Z = R * 0.019334 + G * 0.119193 + B * 0.950227;

// Normalize for D65 white point
X = X / 0.950456;
//Y = Y;
Z = Z / 1.088754;

bool XT, YT, ZT;
if (X > T) XT = true; else XT = false;
if (Y > T) YT = true; else YT = false;
if (Z > T) ZT = true; else ZT = false;

float Y3 = pow(Y, 1 / 3.0);
float fX, fY, fZ;
if (XT) {
fX = pow(X, 1 / 3.0);
} else {
fX = 7.787 * X + 16 / 116;
}
if (YT) {
fY = Y3;
} else {
fY = 7.787 * Y + 16 / 116;
}
if (ZT) {
fZ = pow(Z, 1 / 3.0);
} else {
fZ = 7.787 * Z + 16 / 116;
}

float L;
if (YT) {
L = (116 * Y3) - 16.0;
} else {
L = 903.3 * Y;
}
float a = 500 * (fX - fY);
float b = 200 * (fY - fZ);

//return vec3(L, a, b);
rv3.x = L;
rv3.y = a;
rv3.z = b;
return rv3;
}

VEC3 Lab2RGB(VEC3 lab)
{
VEC3 rv3;
//Thresholds
float T1 = 0.008856;
float T2 = 0.206893;

float X, Y, Z;

//Compute Y
bool XT, YT, ZT;
XT = false;
YT = false;
ZT = false;

float fY = pow(((lab.x + 16.0) / 116.0), 3);
if (fY > T1) {
YT = true;
}
if (YT) {
fY = fY;
} else {
fY = (lab.x / 903.3);
}
Y = fY;

//Alter fY slightly for further calculations
if (YT) {
fY = pow(fY, 1 / 3.0);
} else {
fY = (7.787 * fY + 16.0 / 116.0);
}

//Compute X
float fX = (lab.y / 500.0) + fY;
if (fX > T2) {
XT = true;
}
if (XT) {
X = pow(fX, 3);
} else {
X = ((fX - (16 / 116.0)) / 7.787);
}

//Compute Z
float fZ = fY - (lab.z / 200.0);
if (fZ > T2) {
ZT = true;
}
if (ZT) {
Z = pow(fZ, 3);
} else {
Z = ((fZ - (16 / 116.0)) / 7.787);
}

//Normalize for D65 white point
X = X * 0.950456;
Z = Z * 1.088754;

//XYZ to RGB part
float R = 3.240479 * X + -1.537150 * Y + -0.498535 * Z;
float G = -0.969256 * X + 1.875991 * Y + 0.041556 * Z;
float B = 0.055648 * X + -0.204043 * Y + 1.057311 * Z;

rv3.x = R;
rv3.y = G;
rv3.z = B;
return rv3;
//return vec3(R, G, B);
}

int main(int argc, char **argv)
{
VEC3 v3;
v3.x = 50.0;
v3.y = 50.0;
v3.z = 50.0;
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
v3 = Lab2RGB(v3); // pass copy of v3
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
v3 = RGB2Lab(v3); // pass copy of v3
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
return 0;
}

[guga]

Tks twell

I compiled it for console mode and it works on VS2008. I just needed to change the pow function  to powf due to ambiguity found.

Code Select Expand


// ColorTestConvert.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

/*
int _tmain(int argc, _TCHAR* argv[])
{
return 0;
}
*/


// RGB2LabTest.c for C99
#include <stdio.h>
//#include <stdbool.h>
#include <math.h>

typedef struct _VEC3
{
float x,y,z;
} VEC3, *pvec3;

VEC3 RGB2Lab(VEC3 rgb)
{
VEC3 rv3;
float R = rgb.x;
float G = rgb.y;
float B = rgb.z;
// threshold
float T = 0.008856;

float X = R * 0.412453 + G * 0.357580 + B * 0.180423;
float Y = R * 0.212671 + G * 0.715160 + B * 0.072169;
float Z = R * 0.019334 + G * 0.119193 + B * 0.950227;

// Normalize for D65 white point
X = X / 0.950456;
//Y = Y;
Z = Z / 1.088754;

bool XT, YT, ZT;
if (X > T) XT = true; else XT = false;
if (Y > T) YT = true; else YT = false;
if (Z > T) ZT = true; else ZT = false;

float Y3 = powf(Y, 1 / 3.0);
float fX, fY, fZ;
if (XT) {
fX = powf(X, 1 / 3.0);
} else {
fX = 7.787 * X + 16 / 116;
}
if (YT) {
fY = Y3;
} else {
fY = 7.787 * Y + 16 / 116;
}
if (ZT) {
fZ = powf(Z, 1 / 3.0);
} else {
fZ = 7.787 * Z + 16 / 116;
}

float L;
if (YT) {
L = (116 * Y3) - 16.0;
} else {
L = 903.3 * Y;
}
float a = 500 * (fX - fY);
float b = 200 * (fY - fZ);

//return vec3(L, a, b);
rv3.x = L;
rv3.y = a;
rv3.z = b;
return rv3;
}

VEC3 Lab2RGB(VEC3 lab)
{
VEC3 rv3;
//Thresholds
float T1 = 0.008856;
float T2 = 0.206893;

float X, Y, Z;

//Compute Y
bool XT, YT, ZT;
XT = false;
YT = false;
ZT = false;

float fY = pow(((lab.x + 16.0) / 116.0), 3);
if (fY > T1) {
YT = true;
}
if (YT) {
fY = fY;
} else {
fY = (lab.x / 903.3);
}
Y = fY;

//Alter fY slightly for further calculations
if (YT) {
fY = powf(fY, 1 / 3.0);
} else {
fY = (7.787 * fY + 16.0 / 116.0);
}

//Compute X
float fX = (lab.y / 500.0) + fY;
if (fX > T2) {
XT = true;
}
if (XT) {
X = pow(fX, 3);
} else {
X = ((fX - (16 / 116.0)) / 7.787);
}

//Compute Z
float fZ = fY - (lab.z / 200.0);
if (fZ > T2) {
ZT = true;
}
if (ZT) {
Z = pow(fZ, 3);
} else {
Z = ((fZ - (16 / 116.0)) / 7.787);
}

//Normalize for D65 white point
X = X * 0.950456;
Z = Z * 1.088754;

//XYZ to RGB part
float R = 3.240479 * X + -1.537150 * Y + -0.498535 * Z;
float G = -0.969256 * X + 1.875991 * Y + 0.041556 * Z;
float B = 0.055648 * X + -0.204043 * Y + 1.057311 * Z;

rv3.x = R;
rv3.y = G;
rv3.z = B;
return rv3;
//return vec3(R, G, B);
}

int main(int argc, char **argv)
{
VEC3 v3;
v3.x = 50.0;
v3.y = 50.0;
v3.z = 50.0;
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
v3 = Lab2RGB(v3); // pass copy of v3
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
v3 = RGB2Lab(v3); // pass copy of v3
printf("x= %0.3f, y= %0.3f, z= %0.3f\n", v3.x, v3.y, v3.z);
return 0;
}


[guga]

Ok, guys...both functions are fully working (RGB2Lab and Lab2RGB)

What was missing on the original code is a division of the Red, Green and Blue with 255

I´ll make some other tests and try to implement other matrices for HDTV etc before release them here

Now, it is needed to understand the other functions related to the article posted.