使用cximage可以对图片进行压缩吗?
比如我想把BMP压缩成小一点的JPG
我试了试CxImage image;
// bmp -> jpg
image.Load("image.bmp", CXIMAGE_FORMAT_BMP);
if (image.IsValid()){
if(!image.IsGrayScale()) image.IncreaseBpp(24);
image.SetJpegQuality(99);
image.Save("image.jpg",CXIMAGE_FORMAT_JPG);
}
这段标准代码生成的JPG文件和我BMP文件一样大 郁闷
比如我想把BMP压缩成小一点的JPG
我试了试CxImage image;
// bmp -> jpg
image.Load("image.bmp", CXIMAGE_FORMAT_BMP);
if (image.IsValid()){
if(!image.IsGrayScale()) image.IncreaseBpp(24);
image.SetJpegQuality(99);
image.Save("image.jpg",CXIMAGE_FORMAT_JPG);
}
这段标准代码生成的JPG文件和我BMP文件一样大 郁闷
jpeglib或GDI+
两个我都不会用 不好意思
1. construct Bitmap from HBITMAP2. create IStream in memory
WINOLEAPI CreateStreamOnHGlobal(
HGLOBAL hGlobal,
BOOL fDeleteOnRelease,
LPSTREAM* ppstm
);
3. Save the image to IStream object as JPG.
The following code operates on files, you can rewrite it to realize the feature you needed.
#include <Stdio.h>
#include <Objbase.h>
#include <Windows.h>
#include <Gdiplus.h>
#include <GdiPlusEnums.h>
using namespace Gdiplus;
#pragma comment(lib,"gdiplus")
// Helper functions
int GetCodecClsid(const WCHAR*, CLSID*);int main()
{
CLSID codecClsid;
EncoderParameters encoderParameters;
long quality;
Status stat;
GdiplusStartupInput gdiplusStartupInput;
ULONG gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
{
// Get an image from the disk.
Image image(L"F:\\ddd.bmp");// Get the CLSID of the JPEG codec.
GetCodecClsid(L"image/jpeg", &codecClsid);// Before we call Image::Save, we must initialize an
// EncoderParameters object. The EncoderParameters object
// has an array of EncoderParameter objects. In this
// case, there is only one EncoderParameter object in the array.
// The one EncoderParameter object has an array of values.
// In this case, there is only one value (of type LONG)
// in the array. We will set this value to 0, 50, and 100.encoderParameters.Count = 1;
encoderParameters.Parameter[0].Guid = EncoderQuality;
encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
encoderParameters.Parameter[0].NumberOfValues = 1;// Save the image as a JPEG with quality level 0.
quality = 0;
encoderParameters.Parameter[0].Value = &quality;
stat = image.Save(L"Shapes001.jpg", &codecClsid, &encoderParameters);if(stat == Ok)
wprintf(L"%s saved successfully.\n", L"Shapes001.jpg");
else
wprintf(L"%d Attempt to save %s failed.\n", stat, L"Shapes001.jpg");// Save the image as a JPEG with quality level 50.
quality = 50;
encoderParameters.Parameter[0].Value = &quality;
stat = image.Save(L"Shapes050.jpg", &codecClsid, &encoderParameters);if(stat == Ok)
wprintf(L"%s saved successfully.\n", L"Shapes050.jpg");
else
wprintf(L"%d Attempt to save %s failed.\n", stat, L"Shapes050.jpg");// Save the image as a JPEG with quality level 100.
quality = 100;
encoderParameters.Parameter[0].Value = &quality;
stat = image.Save(L"Shapes100.jpg", &codecClsid, &encoderParameters);if(stat == Ok)
wprintf(L"%s saved successfully.\n", L"Shapes100.jpg");
else
wprintf(L"%d Attempt to save %s failed.\n", stat, L"Shapes100.jpg");
}
GdiplusShutdown(gdiplusToken);
return 0;
} // main
int GetCodecClsid(const WCHAR* format, CLSID* pClsid)
{
UINT num = 0; // number of image encoders
UINT size = 0; // size of the image encoder array in bytesImageCodecInfo* pImageCodecInfo = NULL;GetImageEncodersSize(&num, &size);
if(size == 0)
return -1; // FailurepImageCodecInfo = (ImageCodecInfo*)(malloc(size));
if(pImageCodecInfo == NULL)
return -1; // FailureGetImageEncoders(num, size, pImageCodecInfo);for(int j = 0; j < num; ++j)
{
if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )
{
*pClsid = pImageCodecInfo[j].Clsid;
return j; // Success
}
} // forreturn -1; // Failure} // GetCodecClsid
//download gdiplus.dll
//http://www.microsoft.com/downloads/release.asp?releaseid=32738
//Platform SDK Redistributable: GDI+ R