Qt 图像处理之 灰度变换

对图像的亮度、对比度进行变换是很常用的一种图像处理操作，但是Qt 本身却没有提供相应的功能代码。因此我写了个简单的类来实现这些操作。我把这个类称为 BrightnessMapper。

 

代码如下：

#ifndef BRIGHTNESSMAPPER_H#define BRIGHTNESSMAPPER_H#include <QImage>class BrightnessMapper{public:    BrightnessMapper();    ~BrightnessMapper();    void setRedMap(unsigned char red[]);    void setGreenMap(unsigned char green[]);    void setBlueMap(unsigned char blue[]);    void setMap(unsigned char map[]);    void updateBCG(double brightness, double contrast, double gamma);    void setColorMap(unsigned char red[], unsigned char green[], unsigned char blue[]);    void apply(const QImage &from, QImage &to);    QImage apply(const QImage &from);    unsigned char *redMap(){ return m_red;}    unsigned char *blueMap(){return m_blue;}    unsigned char *greenMap(){return m_green;}    void redMap(double red[256]);    void greenMap(double green[256]);    void blueMap(double blue[256]);private:    unsigned char m_red[256];    unsigned char m_green[256];    unsigned char m_blue[256];};#endif // BRIGHTNESSMAPPER_H

#include "brightnessmapper.h"#include <math.h>#include <QDebug>BrightnessMapper::BrightnessMapper(){    for(int i = 0; i < 256; i++)    {        m_red[i] = i;        m_green[i] = i;        m_blue[i] = i;    }}BrightnessMapper::~BrightnessMapper(){}void BrightnessMapper::updateBCG(double brightness, double contrast, double gamma){    double x, y;    for(int i = 0; i < 256; i ++)    {        x = i / 255.0;        y = exp(log(x) * gamma);        y = (y - 0.5) * brightness + 0.5 + contrast / 255;        y = y * 255.0;        m_red[i] = qBound(0.0, y, 255.0);        m_green[i] = m_red[i];        m_blue[i] = m_red[i];    }}QImage BrightnessMapper::apply(const QImage &from){    QImage to = from;    apply(from, to);    return to;}void BrightnessMapper::apply(const QImage &from, QImage &to){    if(to.size() != from.size() || to.format()!= from.format())    {        to = from.copy();    }    int height = from.height();    int width = from.width();    switch(from.format())    {    case QImage::Format_Indexed8:        for(int i = 0; i < height; i++)        {            const uchar *pFrom = (const uchar *)from.constScanLine(i);            uchar *pTo = (uchar *)to.scanLine(i);            for(int j = 0; j < width; j++)            {                pTo[j] = m_red[pFrom[i]];            }        }        break;    case QImage::Format_RGB32:    case QImage::Format_ARGB32:    case QImage::Format_ARGB32_Premultiplied:        for(int i = 0; i < height; i++)        {            const QRgb *pFrom = (const QRgb *)from.constScanLine(i);            QRgb *pTo = (QRgb *)to.scanLine(i);            for(int j = 0; j < width; j++)            {                int r, g, b;                r = qRed(pFrom[j]);                g = qGreen(pFrom[j]);                b = qBlue(pFrom[j]);                r = m_red[r];                g = m_green[g];                b = m_blue[b];                pTo[j] = qRgb(r, g, b);            }        }        break;    }}void BrightnessMapper::setRedMap(unsigned char red[]){    for(int i = 0; i < 256; i++)    {        m_red[i] = red[i];    }}void BrightnessMapper::setGreenMap(unsigned char green[]){    for(int i = 0; i < 256; i++)    {        m_green[i] = green[i];    }}void BrightnessMapper::setBlueMap(unsigned char blue[]){    for(int i = 0; i < 256; i++)    {        m_blue[i] = blue[i];    }}void BrightnessMapper::setMap(unsigned char map[]){    for(int i = 0; i < 256; i++)    {        m_red[i] = map[i];        m_green[i] = map[i];        m_blue[i] = map[i];    }}void BrightnessMapper::setColorMap(unsigned char red[], unsigned char green[], unsigned char blue[]){    for(int i = 0; i < 256; i++)    {        m_red[i] = red[i];        m_green[i] = green[i];        m_blue[i] = blue[i];    }}void BrightnessMapper::redMap(double red[256]){    for(int i = 0; i < 256; i++)    {        red[i] = m_red[i];    }}void BrightnessMapper::greenMap(double green[256]){    for(int i = 0; i < 256; i++)    {        green[i] = m_green[i];    }}void BrightnessMapper::blueMap(double blue[256]){    for(int i = 0; i < 256; i++)    {        blue[i] = m_blue[i];    }}

这个类的用法很简单。可以用下面几个函数来设置灰度变换关系。

 

void setRedMap(unsigned char red[]);

void setGreenMap(unsigned char green[]);

void setBlueMap(unsigned char blue[]);

void setMap(unsigned char map[]);

void setColorMap(unsigned char red[], unsigned char green[], unsigned char blue[]);

 

也可以用下面这个函数通过设置亮度、对比度、gamma 值来确定变换关系。

void updateBCG(double brightness, double contrast, double gamma);

 

变换关系确定后可以利用下面两个函数之一来对图像进行变换处理。

void apply(const QImage &from, QImage &to);

QImage apply(const QImage &from);

 

还有几个辅助函数可以用来读取变换关系表。

unsigned char *redMap(){ return m_red;}

unsigned char *blueMap(){return m_blue;}

unsigned char *greenMap(){return m_green;}

void redMap(double red[256]);

void greenMap(double green[256]);

void blueMap(double blue[256]);

 

因为代码很简答，就不多介绍了。希望对大家有用。