#include <windows.h>

///////////////////////////////////////////
//
/// Data structure passed from CC3
//

typedef struct
{
	float FilterSettings[10];
	DWORD FilterCustomData[256];
} SETTINGS;

typedef struct
{
	DWORD *pPixels;
	int Width;
	int Height;

	float ViewWidth;
	float ViewHeight;

	SETTINGS *Settings;

	float ViewLowX;
	float ViewLowY;
	float ViewHighX;
	float ViewHighY;			 

	int ViewPixelWidth;
	int ViewPixelHeight;

	void *CopyPixel;		// Address to a function to copy pixels "typedef (__stdcall *T_CopyPixel)(UINT *pDest, UINT *pSrc);"

	// Sun info

	float SunAzimuth;		// Range [0 .. 2*pi)  - The angle to the sun. Mathematical angle (0° along the X-axis, going CCW)
	float SunHeight;		// Range [pi/2 .. pi] - pi/2 is along the horizon, pi is straight up.
	int SunIntensity;		// Range [0 .. 255] 	- The intensity value used for roof shading

} FILTERDATA;

///////////////////////////////////////////
//
/// Possible states
//

#define CMD_FILTER_NAMES         0
#define CMD_HAS_EDIT_DIALOG      1
#define CMD_EDIT_OPTIONS         2
#define CMD_PARAMETER_NAMES      3
#define CMD_SET_DEFAULT_VALUES   4
#define CMD_RUN_FILTER           5
#define CMD_HELP                 6	
#define CMD_WHAT_IS_RETURNED     7 


///////////////////////////////////////////
//
/// The DLL entry point - a good place to init and release memory
//


BOOL APIENTRY DllMain(HANDLE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved)
{
	switch (ul_reason_for_call)
	{
		case DLL_PROCESS_ATTACH:
		case DLL_THREAD_ATTACH:
		case DLL_THREAD_DETACH:
		case DLL_PROCESS_DETACH:
			break;
  }
  return TRUE;
}

///////////////////////////////////////////
//
/// Our filter :-)
//


BOOL ApplyTransparency(FILTERDATA *pData)
{
	DWORD AlphaValue;
	int NumPixels;
	BYTE *p;

	// Convert opacity (in %) to Alpha value
	AlphaValue=(int)(255*pData->Settings->FilterSettings[0]/100);	

	// Make sure it is in range
	if(AlphaValue<1)
		return FALSE;
	if(AlphaValue>255)
		AlphaValue=255;

	// Go through the bitmap and change the alpha value
	p=((BYTE *)pData->pPixels)+3;
	NumPixels=pData->Width*pData->Height;
	while(NumPixels-->0)
	{
		if(*p)
		{
			if(*p==255)
				*p=(BYTE)AlphaValue;
			else 
				*p = (BYTE)(((DWORD)*p * AlphaValue) >> 8);
		}
		p+=4;
	}	 

	return TRUE;
}

///////////////////////////////////////////
//
/// Interface to CC3
//
//
//  Parameters
//
//    Cmd   - The current command
//		Num   - Internal filter number
//    pData - Data structure (only used for CMD_EDIT_OPTIONS, 
//            CMD_SET_DEFAULT_VALUES and CMD_RUN_FILTER)

__declspec(dllexport) unsigned int __stdcall CC2Filter(int Cmd, int Num, FILTERDATA *pData)
{
	switch(Cmd)
	{
		////////////////////////////////////////////////////////////////////////////
		//
		/// Asking for list of filters
		//
		// We should return a string with "Name1\0Name2\0" 

		case CMD_FILTER_NAMES:		
			return (DWORD)"Transparency\0";

		////////////////////////////////////////////////////////////////////////////
		//
		/// Are we doing our own parameters box?
		//
		// Return TRUE if we want to do our own dialog box for options

		case CMD_HAS_EDIT_DIALOG:   
			return FALSE;

		////////////////////////////////////////////////////////////////////////////
		//
		/// Edit our data (if we returned TRUE above)
		//
		// pData has no pixel pointer and the others refer to screen and drawing extents.
		//
		// return TRUE if edit is successful (i.e. user pressed OK)

		case CMD_EDIT_OPTIONS:   
			return FALSE;

		////////////////////////////////////////////////////////////////////////////
		//
		/// Send list of parameter names to edit
		//
		// Return list of strings

		case CMD_PARAMETER_NAMES:  
			switch(Num)
			{
				case 0:
					return (DWORD)"Opacity (%)\0";
			}
			return FALSE;

		////////////////////////////////////////////////////////////////////////////
		//
		/// Set default parameters
		//
		// pData has no pixel pointer and the others refer to screen and drawing extents.

		case CMD_SET_DEFAULT_VALUES:  
			switch(Num)
			{
				case 0:
					pData->Settings->FilterSettings[0]=50;
					break;
			}
			return FALSE;

		////////////////////////////////////////////////////////////////////////////
		//
		/// Apply filter
		//
		// pData set to data for sheet bitmap and size of current view
		//

		case CMD_RUN_FILTER:  
			switch(Num)
			{
				case 0:
					return ApplyTransparency(pData);
			}
			return FALSE;

		////////////////////////////////////////////////////////////////////////////
		//
		/// User pressed help button
		//
		// return FALSE if no help was displayed
		//

		case CMD_HELP:
			return FALSE;

		////////////////////////////////////////////////////////////////////////////
		//
		/// What will the filter return
		//
		// Allowed values:
		// 
		//  0 = complete bitmap (with effect and original)
		//  1 = just the effect. CC3 has to add the original on top later
		//      For exdample shadows and glows uses this. It also forces
		//      these filters to be applied first.


		case CMD_WHAT_IS_RETURNED:
			return 0;
	}


	return 0;
}