?

總結一下個人所知道的使用GDI+縮放圖片的方法.

?

方法一:最簡單的,使用GetThumbnailImage,這個方法的局限性對支持內嵌縮略圖的圖片文件無效. 因為MSDN中提到:如果圖片文件有內嵌的縮略圖,那么就提取這個縮略圖返回,否則就縮放原圖片,不過我想對位圖還是安全的:

Bitmap?* image = new Bitmap(L"MagicLinux.bmp");

Image* pScaledImage = NULL;

UINT nWidth = image->GetWidth()/2;

UINT nHeight= image->GetHeight()/2;

pScaledImage = image->GetThumbnailImage(nWidth, nHeight, NULL, NULL);

delete pScaledImage;

delete image;

?

方法二,使用Graphics::DrawImage,這樣還可以控制InterpolationMode(插值模式,在縮放和旋轉時候使用),即可以控制縮放質量高低.也可以通過Graphics對象做其他的控制.

方法也比較簡單,但是卻費了我好久時間才研究出來,沒辦法,不熟悉GDI+,在MSDN中翻來翻去,:)

Bitmap * ScaleBitmap(Bitmap * pBitmap,UINT nWidth,UINT nHeight)

{

Bitmap * pTemp = new Bitmap(nWidth,nHeight,pBitmap->GetPixelFormat());

if( pTemp )

{

Graphics * g = Graphics::FromImage(pTemp);

if( g )

{

// use the best interpolation mode

g->SetInterpolationMode(InterpolationModeHighQualityBicubic);

g->DrawImage(pBitmap,0,0,nWidth,nHeight);

delete g;

}

}

return pTemp;

}

pScaledImage = ScaleBitmap(image,nWidth,nHeight);

?

方法三,是從Codeguru上一個帖子上看到,和方法二類似,但是用了GDI的東東,我試了試,沒成功,得到的是一幅黑圖片,可能的原因是Bitmap::FromHBITMAP的第二個參數設置不對

原文代碼如下:

Bitmap * bitmap = new Bitmap(TempBuf); // Create the bitmap

HDC Screen = GetDC(WindowVars.Handle);

piTemp->hdc = CreateCompatibleDC(Screen); // Create a memory DC

HBITMAP hbitmap;

if (bStretchPictures)

hbitmap = CreateCompatibleBitmap(Screen, Size.X, Size.Y);

else

hbitmap = CreateCompatibleBitmap(Screen, bitmap->GetWidth(), bitmap->GetHeight());

SelectObject(piTemp->hdc, hbitmap); // Initialize the DC

Graphics * graphics = new Graphics(piTemp->hdc); // Create the Graphics class

if (bStretchPictures)

graphics->DrawImage(bitmap, 0, 0, Size.X, Size.Y); // Draw the scaled image

else

graphics->DrawImage(bitmap, 0, 0, bitmap->GetWidth(), bitmap->GetHeight());

ReleaseDC(WindowVars.Handle, Screen);

delete graphics;

delete bitmap;

?

?

另外再補上保存圖片的代碼:

?

bool SaveAsImageFile(Image * pImage,LPCWSTR lpszFileName,LPCWSTR lpszImageType)

{

?

UINT?num = 0;

?

// number of image encoders

UINT?size = 0;

?

// size of the image encoder array in bytes

ImageCodecInfo* pImageCodecInfo = NULL;

?

if(GetImageEncodersSize(&num, &size)!= Ok || size == 0 )

return false;?// Failure

?

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

if(pImageCodecInfo == NULL)

return false;?// Failure

?

if(GetImageEncoders(num, size, pImageCodecInfo)!= Ok )

return false;

?

bool bOk = false;

for(UINT j = 0; j < num; ++j)

{

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

{

pImage->Save(lpszFileName,&(pImageCodecInfo[j].Clsid));

bOk = true;

break;

}

?

}

?

free(pImageCodecInfo);

return bOk;

?

}

?

調用象這樣就可以保存成各種圖片(當然要求有對應的encoder才行):

SaveAsImageFile(pScaledImage,L"1.bmp",L"image/bmp");

SaveAsImageFile(pScaledImage,L"1.jpg",L"image/jpeg");

SaveAsImageFile(pScaledImage,L"1.png",L"image/png");

轉載于:https://www.cnblogs.com/loveme513/archive/2006/05/10/395990.html

總結

以上是生活随笔為你收集整理的使用GDI+缩放图片文件的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。