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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。其中包含了尺寸和质量两种压缩算法,并且支持JPEG、bmp、PNG等格式。今天把这段逻辑贴出来,供大家参考。(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 = http://www.mamicode.com/&quality;> 这两个算法,都关联了一个函数GetEncoderClsid,其实现是:
#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 }在我的测试代码中,文件名中包含A的为源文件,文件名中包含B的是尺寸压缩算法得到的文件,文件名中包含C的是质量压缩(尺寸不变)算法得到的文件。测试代码是
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。如果想通过压缩算法控制文件大小,需要结合这两种方法。但是需要指出的是,该质量压缩算法不可以滥用。因为在一定情况下,该质量压缩会使文件空间大小变大。
最后附上工程代码。
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