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Converting between different image formats (using GDI+)

, 5 Jan 2011 CPOL
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Shows how to convert between different image formats by using GDI+
Given an input stream of some type of image, the following function converts that image into another type of image given the destination format. The destination format should be a proper mime-type such as "image/jpeg", "image/png".
Gdiplus::Status imageToImage(
  IStream *pStreamIn, IStream *pStreamOut, BSTR wszOutputMimeType)
    namespace G = Gdiplus;
    G::Status status = G::Ok;
    G::Image imageSrc(pStreamIn);
    status = imageSrc.GetLastStatus();
    if (G::Ok != status) {
      return status;
    UINT numEncoders = 0;
    UINT sizeEncodersInBytes = 0;
    status = G::GetImageEncodersSize(&numEncoders, &sizeEncodersInBytes);
    if (status != G::Ok) {
      return status;
    G::ImageCodecInfo *pImageCodecInfo = 
         (G::ImageCodecInfo *) malloc(sizeEncodersInBytes);
    status = G::GetImageEncoders(
          numEncoders, sizeEncodersInBytes, pImageCodecInfo);
    if (status != G::Ok) {
      return status;
    CLSID clsidOut;
    status = G::UnknownImageFormat;
    for (UINT j = 0; j < numEncoders; j ++) {
      if (0 == wcscmp(pImageCodecInfo[j].MimeType, wszOutputMimeType)) {
        clsidOut = pImageCodecInfo[j].Clsid;
        status = G::Ok;
    if (status != G::Ok) {
      return status;
    return imageSrc.Save(pStreamOut, &clsidOut);
It can be used like so:
extern IStream *pSomeImg; // source image format is not important
extern IStream *pMyJpeg;
if (Gdiplus::Ok == imageToImage(pSomeImg, pMyJpeg, L"image/jpeg")) {
// pMyJpeg holds the converted jpeg.
If there is a need to put/retrieve data into/from IStream in byte-array format (such as char*), it can by done by using CreateStreamOnHGlobal, GlobalAlloc, GlobalLock Win32 API functions. See this tip for more details.

Note: List of supported formats: BMP, ICON, GIF, JPEG, Exif, PNG, TIFF, WMF, and EMF.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Arman S.
Software Developer 13
United States United States
No Biography provided

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