From Tracker Software PDF SDK
FillChannel fills a specified rectangle of the page with a specified color value into one specified color channel.
HRESULT FillChannel([in] IXC_Channel nDstChannel, [in] UCHAR nValue, [in] RECT* stRect);
- [in] Specifies color channel which will be used.
- [in] Specifies the value which will be filled with. Possible value is from 0 to 255.
- [in] Pointer to RECT structure which defines the area to be filled.
Returns S_OK if operation was successful or error code in other cases.