XPS OM-Farbverläufe

Dieses Thema enthält ein Beispiel für die Verwendung von Farbverläufen in einem XPS OM.

Hinzufügen eines neuen Stopps zu einem vorhandenen Farbverlauf

Im folgenden Codebeispiel wird dem Farbverlauf eines Pinsels mit linearem Farbverlauf ein neuer Stopp hinzugefügt.

    // brush is the pointer to the gradient brush that will get 
    //  the new gradient and is initialized outside of this code example

    // this is the start of the method that updates the brush
    HRESULT                           hr = S_OK;
    XPS_COLOR                         xpsColorStop;
    IXpsOMGradientStopCollection      *stops;
    IXpsOMGradientStop                *xpsNewGradientStop = NULL, *thisStop = NULL, *nextStop = NULL;
    UINT32                            thisStopIdx, numStops;
    FLOAT                             thisStopOffset, nextStopOffset, newStopOffset;
    BOOL                              bUpdated = FALSE;

    // define the new stop color to be yellow
    xpsColorStop.colorType        = XPS_COLOR_TYPE_SRGB;
    xpsColorStop.value.sRGB.alpha = 0xFF;
    xpsColorStop.value.sRGB.red   = 0xFF;
    xpsColorStop.value.sRGB.green = 0xFF;
    xpsColorStop.value.sRGB.blue  = 0x00;
    
    // create a new gradient stop by setting the color and location 
    // this stop will be half way between the start and end point
    newStopOffset = 0.5f;
    hr = xpsFactory->CreateGradientStop(&xpsColorStop, NULL, newStopOffset, &xpsNewGradientStop);

    // get the collection of gradient stops from the brush
    hr = brush->GetGradientStops (&stops);

    hr = stops->GetCount (&numStops);
    // there will never be less than two stops
    
    // insert the new stop so that the stops are sorted by offset
    // if an existing stop has the same offset as the new one,
    // overwrite the existing stop with the new stop.
    for (thisStopIdx = 0; thisStopIdx < (numStops-1); thisStopIdx++) {
        hr = stops->GetAt(thisStopIdx, &thisStop);
        hr = stops->GetAt(thisStopIdx+1, &nextStop);
    
        hr = thisStop->GetOffset (&thisStopOffset);
        hr = nextStop->GetOffset (&nextStopOffset);

        if (newStopOffset < thisStopOffset) {
            // insert at thisStopIdx
            stops->InsertAt(thisStopIdx, xpsNewGradientStop);
            bUpdated = TRUE;
            break; // done, so leave loop
        } 
        if ((newStopOffset > thisStopOffset) && (newStopOffset < nextStopOffset)) {
            // the new stop goes in between them
            stops->InsertAt (thisStopIdx+1, xpsNewGradientStop);
            bUpdated = TRUE;
            break; // done, so leave loop
        } 

        if (newStopOffset == thisStopOffset ) {
            // then overwrite the old one
            stops->SetAt (thisStopIdx, xpsNewGradientStop);
            bUpdated = TRUE;
            break; // done, so leave loop
        }

        if (newStopOffset == nextStopOffset ) {
            // then overwrite the old one
            stops->SetAt (thisStopIdx+1, xpsNewGradientStop);
            bUpdated = TRUE;
            break; // done, so leave loop
        }

        // on the last entry, see if this stop is greater than the last entry
        // in the collection. If so, append the new one to the end.
        if ((thisStopIdx == (numStops-2)) && (newStopOffset > nextStopOffset )) {
            // then overwrite the old one
            stops->Append ( xpsNewGradientStop );
            bUpdated = TRUE;
            break; // done, so leave loop
        }
        if (NULL != thisStop) {thisStop->Release(); thisStop = NULL;}
        if (NULL != nextStop) {nextStop->Release(); nextStop = NULL;}
    }
    if (NULL != thisStop) {thisStop->Release(); thisStop = NULL;}
    if (NULL != nextStop) {nextStop->Release(); nextStop = NULL;}

    // make sure that the new stop was put somewhere in the collection
    _ASSERT (bUpdated);
    return S_OK;

Zugehörige Themen

IXpsOMGradientStop-Schnittstelle

IXpsOMGradientStopCollection-Schnittstelle