contrastprocess.cpp

visual c++数字图像与图形处理中的光盘内容

/////////////////////////////////////////////////////////////////////////////////
//
// ContrastProcess.cpp: implementation of the CContrastProcess class.
//
////////////////////////////////////////////////////////////////////////////////
// 版权所有(2002)
// Copyright(2002)
// 编写者: 向世明
// Author: Xiang Shiming


#include "stdafx.h"
#include "ContrastProcess.h"


//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

IMPLEMENT_DYNAMIC(CContrastProcess, CImagePointProcess)
CContrastProcess::CContrastProcess()
{
	m_dwOperation = IMAGE_CONTRAST_ADJUSTMENT;
	m_nIncrement = 0;
}

CContrastProcess::~CContrastProcess()
{

}

#ifdef _DEBUG
void CContrastProcess::Dump(CDumpContext& dc) const
{
	CImagePointProcess::Dump(dc);
}

void CContrastProcess::AssertValid() const
{
	CImagePointProcess::AssertValid();
}
#endif


void CContrastProcess::SetContrastIncrement(int nIncrement)
{
	m_nIncrement = nIncrement;
}

//增加对比度
void CContrastProcess::IncreaseContrast(BYTE *pbyBlue,  BYTE *pbyGreen,  BYTE *pbyRed, int nHigh, int nStretch)
{
	//in this case, m_nIncrement >= 0
	//nStretch = 255 - 2 * m_nIncrement;
	//high = 255 - m_nIncrement;

	//线性扩展
	//蓝色
	if(*pbyBlue <= m_nIncrement) *pbyBlue = 0;
	else if(*pbyBlue > nHigh) *pbyBlue = 255;
	else
		*pbyBlue = (BYTE)((((int)*pbyBlue - m_nIncrement) * 255) / nStretch );

	//绿色
	if(*pbyGreen <= m_nIncrement) *pbyGreen = 0;
	else if(*pbyGreen > nHigh) *pbyGreen = 255;
	else
		*pbyGreen = (BYTE)((((int)*pbyGreen - m_nIncrement) * 255) / nStretch );
	
	//红色
	if(*pbyRed <= m_nIncrement) *pbyRed = 0;
	else if(*pbyRed > nHigh) *pbyRed = 255;
	else
		*pbyRed = (BYTE)((((int)*pbyRed - m_nIncrement) * 255) / nStretch );
}

void CContrastProcess::DecreaseContrast(BYTE *pbyBlue,  BYTE *pbyGreen,  BYTE *pbyRed, int nStretch)
{
	//in this case m_nIncrement < 0
	//nStretch = 255 + 2 * m_nIncrement;
	
	//线性压缩
	*pbyBlue = (BYTE)((((int)(*pbyBlue) * nStretch) / 255) - m_nIncrement);
	*pbyGreen = (BYTE)((((int)(*pbyGreen) * nStretch) / 255) - m_nIncrement);
	*pbyRed = (BYTE)((((int)(*pbyRed) * nStretch) / 255) - m_nIncrement);
}

//改变指定区域(x, y, nWidth, nHeight)的对比度.
//nScanWidth表示数据扫描宽度, 以像素为单位, 而不是以字节为单位
//nScanHeight表示可扫描高度, 该参数主要用于合法性检验, 保证被处理的区域是合法区域.
//lpbyBits32--源数据----32位
//本来, 处理成DWORD数据最直观, 但显然速度没有BYTE快
//对应的DWORD格式应为A--R--G--B(从高位到低位), 这与通用的标准是一致的, 如Java

//BYTE型数据格式(依次):	B--G--R--A


BOOL CContrastProcess::ChangeContrast(LPBYTE lpbyBits32,  int x,  int y,  int nWidth,  int nHeight,  int nScanWidth,  int nScanHeight)
{
	ASSERT(lpbyBits32);
	//第一步, 进行参数合法性检测
	if((x > (nScanWidth - 1)) || (y > (nScanHeight - 1))) return FALSE;
	//有效区域的宽度和高度
	int w = min(nWidth, nScanWidth - x);
	int h = min(nHeight, nScanHeight - y);

	//行字节数
	DWORD dwWidthBytes = (DWORD)nScanWidth * 4;

	//开始数据基索引
	DWORD dwBaseIndex = y * dwWidthBytes + 4 * x;

	//第二步, 对比度修改

	//被扩展或压缩到的区间的左端点
	int nHigh = 255 - m_nIncrement;

	//对于极端情况加以处理
	if(nHigh < m_nIncrement)
	{
		nHigh = 127;
		m_nIncrement = 120;
	}
	if(m_nIncrement < -127)m_nIncrement = -120;

	//扩展或压缩区间的长度
	int nStretch = 255;
	if(m_nIncrement >= 0)
		nStretch = 255 - 2 * m_nIncrement;
	else
		nStretch = 255 + 2 * m_nIncrement;

	for(int i = 0;i < h;i++)
	{
		BYTE* pbyRsc = lpbyBits32 + dwBaseIndex;

		for(int j = 0;j < w;j++)
		{
			BYTE* pbyBlue = pbyRsc++;
			BYTE* pbyGreen = pbyRsc++;
			BYTE* pbyRed = pbyRsc++;
			pbyRsc++;
			if(m_nIncrement >= 0)
				IncreaseContrast(pbyBlue, pbyGreen, pbyRed, nHigh, nStretch);
			else
				DecreaseContrast(pbyBlue, pbyGreen, pbyRed, nStretch);
		}
		dwBaseIndex += dwWidthBytes;
	}
	return TRUE;
}