IWICProgressiveLevelControl::GetLevelCount method (wincodec.h)

Gets the number of levels of progressive decoding supported by the CODEC.

Syntax

HRESULT GetLevelCount(
  [out, retval] UINT *pcLevels
);

Parameters

[out, retval] pcLevels

Type: UINT*

Indicates the number of levels supported by the CODEC.

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

Users should not use this function to iterate through the progressive levels of a progressive JPEG image. JPEG progressive levels are determined by the image and do not have a fixed level count. Using this method will force the application to wait for all progressive levels to be downloaded before it can return. Instead, applications should use the following code to iterate through the progressive levels of a progressive JPEG image.

Examples

IWICProgressiveLevelControl *pProgressive = NULL;

HRESULT hr = (pBitmapFrame->QueryInterface(
   IID_IWICProgressiveLevelControl, 
   (void**) &pProgressive));
                
if (SUCCEEDED(hr))
{
   for (UINT uCurrentLevel = 0; SUCCEEDED(hr); uCurrentLevel++)
   {
      hr = pProgressive->SetCurrentLevel(uCurrentLevel);
      if (WINCODEC_ERR_INVALIDPROGRESSIVELEVEL == hr)
      {
         // No more levels
         break;
      }

      if (SUCCEEDED(hr))
      {
         // Output the current level
         hr = pBitmapFrame->CopyPixels(...);
      }                      
   }
}

if (pProgressive)
{
   pProgressive->Release();
}

Requirements

See also

IWICProgressiveLevelControl

Progressive Decoding Overview