将各种格式的图像转换为灰度图像

接着上一篇的程序。下面的一个功能是利用FreeImage将各种格式的图像转换为灰度图像。

方法一：自己写转换函数；

下面的代码就是将各种编码格式的图像转化为灰度图像的处理函数：

    FIBITMAP* CGenricImageTransformerView::TransformToGrayscale(FIBITMAP *dib)  
    {  
        const int nBitCounts = 8;  
        int nBpp = FreeImage_GetBPP(dib);  
        BYTE* imgData = FreeImage_GetBits(dib);  
        int width = FreeImage_GetWidth(dib);  
        int height = FreeImage_GetHeight(dib);  
        FIBITMAP* fiBmp = FreeImage_Allocate(width,height,nBitCounts);  
        RGBQUAD* pRGBTable = FreeImage_GetPalette(fiBmp);  
        //创建灰度索引调色板  
        for (int i = 0;i<256;i++)  
        {  
            pRGBTable[i].rgbBlue = i;  
            pRGBTable[i].rgbGreen = i;  
            pRGBTable[i].rgbRed = i;  
        }  
        BYTE nIntensity;  
        int j,k;  
        switch(nBpp)  
        {  
        case 32:        //32位图（带alpha通道）转换为8位灰度图  
            for(j=0;j<height;j++)  
            {  
                for(k=0;k<4*width;k++)  
                {  
                    nIntensity = (BYTE)(0.299*imgData[j*4*width+k]+  
                        0.587*imgData[j*4*width+k+1]+0.114*imgData[j*4*width+k+2]);  
                    if(k%4)  
                        FreeImage_SetPixelIndex(fiBmp,k/4,j,&nIntensity);  
                }  
            }  
            return fiBmp;  
        break;  
        case 24:        //24位图像转为8位灰度图    
            for(j=0;j<height;j++)  
            {  
                for(k=0;k<3*width;k++)  
                {  
                    nIntensity = (BYTE)(0.299*imgData[j*3*width+k]+  
                            0.587*imgData[j*3*width+k+1]+0.114*imgData[j*3*width+k+2]);  
                    if(k%3)  
                        FreeImage_SetPixelIndex(fiBmp,k/3,j,&nIntensity);  
                }  
            }  
            return fiBmp;  
        break;  
        case 8:     //8位伪彩色转为8位灰度图  
            for(j=0;j<height;j++)  
            {  
                for(k=0;k<width;k++)  
                {  
                    FreeImage_GetPixelIndex(dib,k,j,&nIntensity);  
                    RGBQUAD* ptrRGB = FreeImage_GetPalette(dib);  
                    nIntensity = (BYTE)(0.299*ptrRGB[nIntensity].rgbRed+  
                        0.587*ptrRGB[nIntensity].rgbGreen+0.114*ptrRGB[nIntensity].rgbBlue);  
                    FreeImage_SetPixelIndex(fiBmp,k,j,&nIntensity);  
                }  
            }  
            return fiBmp;  
        break;  
        default:  
            break;  
        }  
        return NULL; 

在菜单栏中新建一个菜单项，设置标签为：转换为灰度图像，并添加命令处理函数：

    void CGenricImageTransformerView::OnTransformToGrayscale()   
    {  
        // TODO: Add your command handler code here  
        FIBITMAP* fiBitmap = TransformToGrayscale(dib);  
        CFileDialog fileDlg(FALSE,".bmp","img.*",OFN_HIDEREADONLY|OFN_OVERWRITEPROMPT,  
                            "bmp(*.bmp)|*.bmp|jpg(*.jpg)|*.jpg|/  
                            tif(*.tif)|*.tif|png(*.png)|*.png|/  
                            gif(*.gif)|*.gif|Any(*.*)|*.*||",  
                             NULL);  

        if(IDOK == fileDlg.DoModal())  
        {  
            CString filename = fileDlg.GetFileName();  
            BOOL bSuccess = GenericWriter(fiBitmap,filename);  
            if(!bSuccess)  
                MessageBox("Not support that type!"); 

方法二：直接调用FreeImage库中已经定义好的转换函数：

   void CGenricImageTransformerView::OnTransformToGrayscale()   
    {  
        // TODO: Add your command handler code here  
        FIBITMAP* fiBitmap =FreeImage_ConvertToGrayscale(dib);//这里调用FreeImage库中的转换为灰度的函数  
        CFileDialog fileDlg(FALSE,".bmp","img.*",OFN_HIDEREADONLY|OFN_OVERWRITEPROMPT,  
                            "bmp(*.bmp)|*.bmp|jpg(*.jpg)|*.jpg|/  
                            tif(*.tif)|*.tif|png(*.png)|*.png|/  
                            gif(*.gif)|*.gif|Any(*.*)|*.*||",  
                             NULL);  

        if(IDOK == fileDlg.DoModal())  
        {  
            CString filename = fileDlg.GetFileName();  
            BOOL bSuccess = GenericWriter(fiBitmap,filename);  
            if(!bSuccess)  
                MessageBox("Not support that type!");  
        }  

    }  

用起来也特别方便，除此之外，FreeImage提供了其他的转换函数，可以转换为4位、8位、16位、24位、32位等图像类型。

原文地址：http://blog.csdn.net/summersolstice/article/details/5161859