一种使用GDI+对图片尺寸和质量的压缩方法

今天同事向我询问图片压缩的算法。我想起大概两三年前做过的一个项目。

当中包括了尺寸和质量两种压缩算法。而且支持JPEG、bmp、PNG等格式。

今天把这段逻辑贴出来，供大家參考。（转载请指明来源于breaksoftware的CSDN博客）

尺寸压缩

bool CompressImagePixel(

    const WCHAR* pszOriFilePath,

    const WCHAR* pszDestFilePah,

    UINT ulNewHeigth,

    UINT ulNewWidth )

{

    // Initialize GDI+.

    GdiplusStartupInput gdiplusStartupInput;

    ULONG_PTR gdiplusToken;

    Status stat = GenericError;

    stat = GdiplusStartup( &gdiplusToken, &gdiplusStartupInput, NULL );

    if ( Ok != stat ) {

        return false;

    }

    // 重置状态

    stat = GenericError;

    // Get an image from the disk.

    Image* pImage = new Image(pszOriFilePath);

    do {

        if ( NULL == pImage ) {

            break;

        }

        // 获取长宽

        UINT unOriHeight = pImage->GetHeight();

        UINT unOriWidth = pImage->GetWidth();

        do {

            CLSID encoderClsid;

            if ( unOriWidth < 1 || unOriHeight < 1 ) {

                break;

            }

            // Get the CLSID of the JPEG encoder.

            if ( !GetEncoderClsid(L"image/jpeg", &encoderClsid) ) {

                break;

            }

            REAL fSrcX = 0.0f;

            REAL fSrcY = 0.0f;

            REAL fSrcWidth = (REAL) unOriWidth;

            REAL fSrcHeight = (REAL) unOriHeight ;

            RectF RectDest( 0.0f, 0.0f, (REAL)ulNewWidth, (REAL)ulNewHeigth);

            Bitmap* pTempBitmap = new Bitmap( ulNewWidth, ulNewHeigth );

            Graphics* graphics = NULL;

            do {

                if ( !pTempBitmap ) {

                    break;

                }

                graphics = Graphics::FromImage( pTempBitmap );

                if ( !graphics ) {

                    break;

                }

                stat = graphics->SetInterpolationMode(Gdiplus::InterpolationModeHighQuality);

                if ( Ok != stat ) {

                    break;

                }

                stat = graphics->SetSmoothingMode(Gdiplus::SmoothingModeHighQuality);

                if ( Ok != stat ) {

                    break;

                }

                stat = graphics->DrawImage( pImage, RectDest, fSrcX, fSrcY, fSrcWidth, fSrcHeight,

                    UnitPixel, NULL, NULL, NULL);

                if ( Ok != stat ) {

                    break;

                }

                stat = pTempBitmap->Save( pszDestFilePah, &encoderClsid, NULL );

                if ( Ok != stat ) {

                    break;

                }

            } while(0);

            if ( NULL != graphics ) {

                delete graphics;

                graphics = NULL;

            }

            if ( NULL != pTempBitmap ) {

                delete pTempBitmap;

                pTempBitmap = NULL;

            }

        } while(0);

    } while (0);

    if ( pImage ) {

        delete pImage;

        pImage = NULL;

    }

    GdiplusShutdown(gdiplusToken);

    return ( ( Ok == stat ) ? true : false );

}

质量压缩

bool CompressImageQuality(

    const WCHAR* pszOriFilePath,

    const WCHAR* pszDestFilePah,

    ULONG quality )

{

    // copy from http://msdn.microsoft.com/en-us/library/ms533844(v=VS.85).aspx

    // Initialize GDI+.

    GdiplusStartupInput gdiplusStartupInput;

    ULONG_PTR gdiplusToken;

    Status stat = GenericError;

    stat = GdiplusStartup( &gdiplusToken, &gdiplusStartupInput, NULL );

    if ( Ok != stat ) {

        return false;

    }

    // 重置状态

    stat = GenericError;

    // Get an image from the disk.

    Image* pImage = new Image(pszOriFilePath);

    do {

        if ( NULL == pImage ) {

            break;

        }

        // 获取长宽

        UINT ulHeight = pImage->GetHeight();

        UINT ulWidth = pImage->GetWidth();

        if ( ulWidth < 1 || ulHeight < 1 ) {

            break;

        }

        // Get the CLSID of the JPEG encoder.

        CLSID encoderClsid;

        if ( !GetEncoderClsid(L"image/jpeg", &encoderClsid) ) {

            break;

        }

        // The one EncoderParameter object has an array of values.

        // In this case, there is only one value (of type ULONG)

        // in the array. We will let this value vary from 0 to 100.

        EncoderParameters encoderParameters;

        encoderParameters.Count = 1;

        encoderParameters.Parameter[0].Guid = EncoderQuality;

        encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;

        encoderParameters.Parameter[0].NumberOfValues = 1;

        encoderParameters.Parameter[0].Value = &quality;

        stat = pImage->Save(pszDestFilePah, &encoderClsid, &encoderParameters);

    } while(0);

    if ( pImage ) {

        delete pImage;

        pImage = NULL;

    }

    GdiplusShutdown(gdiplusToken);

    return ( ( stat == Ok ) ? true : false );

}

这两个算法，都关联了一个函数GetEncoderClsid，事实上现是：

#include <Windows.h>

#include <GdiPlus.h>

#pragma comment( lib, "GdiPlus.lib" )

using namespace Gdiplus;

bool GetEncoderClsid(const WCHAR* pszFormat, CLSID* pClsid)

{

    UINT  unNum = 0;          // number of image encoders

    UINT  unSize = 0;         // size of the image encoder array in bytes

    ImageCodecInfo* pImageCodecInfo = NULL;

    // How many encoders are there?

    // How big (in bytes) is the array of all ImageCodecInfo objects?

    GetImageEncodersSize( &unNum, &unSize );

    if ( 0 == unSize ) {

        return false;  // Failure

    }

    // Create a buffer large enough to hold the array of ImageCodecInfo

    // objects that will be returned by GetImageEncoders.

    pImageCodecInfo = (ImageCodecInfo*)( malloc(unSize) );

    if ( !pImageCodecInfo ) {

        return false;  // Failure

    }

    // GetImageEncoders creates an array of ImageCodecInfo objects

    // and copies that array into a previously allocated buffer.

    // The third argument, imageCodecInfos, is a pointer to that buffer.

    GetImageEncoders( unNum, unSize, pImageCodecInfo );

    for ( UINT j = 0; j < unNum; ++j ) {

        if ( wcscmp( pImageCodecInfo[j].MimeType, pszFormat ) == 0 ) {

            *pClsid = pImageCodecInfo[j].Clsid;

            free(pImageCodecInfo);

            pImageCodecInfo = NULL;

            return true;  // Success

        }

    }

    free( pImageCodecInfo );

    pImageCodecInfo = NULL;

    return false;  // Failure

}

在我的測试代码中，文件名称中包括A的为源文件，文件名称中包括B的是尺寸压缩算法得到的文件，文件名称中包括C的是质量压缩（尺寸不变）算法得到的文件。測试代码是

int _tmain(int argc, _TCHAR* argv[])

{

    CompressImagePixel( L"1A.jpg", L"1B.jpg",  100, 100 );

    CompressImageQuality( L"1A.jpg", L"1C.jpg", 30 );

    CompressImagePixel( L"2A.png", L"2B.jpg",  100, 100 );

    CompressImageQuality( L"2A.png", L"2C.jpg", 30 );

    CompressImagePixel( L"3A.bmp", L"3B.jpg",  100, 100 );

    CompressImageQuality( L"3A.bmp", L"3C.jpg", 30 );

	return 0;

}

其压缩结果是

从压缩结果看。尺寸压缩是稳定的。质量压缩是不稳定的。假设想通过压缩算法控制文件大小，须要结合这两种方法。可是须要指出的是。该质量压缩算法不能够滥用。由于在一定情况下，该质量压缩会使文件空间大小变大。

最后附上project代码。

巴特西

一种使用GDI+对图片尺寸和质量的压缩方法

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