/** 
 * @file llviewerlayer.cpp
 * @brief LLViewerLayer class implementation
 *
 * $LicenseInfo:firstyear=2002&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#include "llviewerprecompiledheaders.h"

#include "llviewerlayer.h"
#include "llerror.h"
#include "llmath.h"

LLViewerLayer::LLViewerLayer(const S32 width, const F32 scale)
{
	mWidth = width;
	mScale = scale;
	mScaleInv = 1.f/scale;
	mDatap = new F32[width*width];

	for (S32 i = 0; i < width*width; i++)
	{
		*(mDatap + i) = 0.f;
	}
}

LLViewerLayer::~LLViewerLayer()
{
	delete[] mDatap;
	mDatap = NULL;
}

F32 LLViewerLayer::getValue(const S32 x, const S32 y) const
{
//	llassert(x >= 0);
//	llassert(x < mWidth);
//	llassert(y >= 0);
//	llassert(y < mWidth);

	return *(mDatap + x + y*mWidth);
}

F32 LLViewerLayer::getValueScaled(const F32 x, const F32 y) const
{
	S32 x1, x2, y1, y2;
	F32 x_frac, y_frac;

	x_frac = x*mScaleInv;
	x1 = llfloor(x_frac);
	x2 = x1 + 1;
	x_frac -= x1;

	y_frac = y*mScaleInv;
	y1 = llfloor(y_frac);
	y2 = y1 + 1;
	y_frac -= y1;

	x1 = llmin((S32)mWidth-1, x1);
	x1 = llmax(0, x1);
	x2 = llmin((S32)mWidth-1, x2);
	x2 = llmax(0, x2);
	y1 = llmin((S32)mWidth-1, y1);
	y1 = llmax(0, y1);
	y2 = llmin((S32)mWidth-1, y2);
	y2 = llmax(0, y2);

	// Take weighted average of all four points (bilinear interpolation)
	S32 row1 = y1 * mWidth;
	S32 row2 = y2 * mWidth;
	
	// Access in squential order in memory, and don't use immediately.
	F32 row1_left  = mDatap[ row1 + x1 ];
	F32 row1_right = mDatap[ row1 + x2 ];
	F32 row2_left  = mDatap[ row2 + x1 ];
	F32 row2_right = mDatap[ row2 + x2 ];
	
	F32 row1_interp = row1_left - x_frac * (row1_left - row1_right);
	F32 row2_interp = row2_left - x_frac * (row2_left - row2_right);
	
	return row1_interp - y_frac * (row1_interp - row2_interp);
}
