GDI/图象编程

开发平台：
Visual C++

ChangeBmp.cpp：源码内容
							// ChangeBmp.cpp : 实现文件
//
#include "stdafx.h"
#include "GandyDraw.h"
#include "ChangeBmp.h"
// CChangeBmp 对话框
IMPLEMENT_DYNAMIC(CChangeBmp, CDialog)
CChangeBmp::CChangeBmp(CWnd* pParent /*=NULL*/)
	: CDialog(CChangeBmp::IDD, pParent)
	, m_iShowWidth(0)
	, m_iShowHeight(0)
	, m_BmpPathName(_T(""))
{
	m_FileBitmap.LoadBitmapW(IDB_BITMAP_MM);
}
CChangeBmp::~CChangeBmp()
{
}
void CChangeBmp::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	DDX_Text(pDX, IDC_SHOW_WIDTH, m_iShowWidth);
	DDX_Text(pDX, IDC_SHOW_HEIGHT, m_iShowHeight);
}
BEGIN_MESSAGE_MAP(CChangeBmp, CDialog)
	ON_BN_CLICKED(IDC_LOADBMP, &CChangeBmp::OnBnClickedLoadbmp)
	ON_WM_PAINT()
END_MESSAGE_MAP()
// CChangeBmp 消息处理程序
void CChangeBmp::OnBnClickedLoadbmp()
{
	wchar_t filters[] = L"位图文件(*.bmp)|*.bmp|所有文件(*.*)|*.*||";
	CFileDialog fileDlg(TRUE, NULL, NULL, OFN_HIDEREADONLY, filters);
	if (fileDlg.DoModal() == IDOK) 
	{
		HBITMAP hBmp = (HBITMAP)LoadImage(NULL, fileDlg.GetPathName(), 
			IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | 
			LR_DEFAULTCOLOR | LR_DEFAULTSIZE);
		if (hBmp != NULL) {
			BITMAP bm;
			GetObject(hBmp, sizeof(bm), &bm);
			long cb = bm.bmBitsPixel * bm.bmHeight * bm.bmWidthBytes;
			bm.bmBits = new char[cb];
			GetBitmapBits(hBmp, cb, bm.bmBits);
			m_FileBitmap.CreateBitmapIndirect(&bm);
			m_BmpPathName = fileDlg.GetPathName();
			//m_bBitmapLoaded = true;
		}
	}
	//BITMAP bs;
	//m_FileBitmap.GetBitmap(&bs);
	//m_iShowWidth = bs.bmWidth;
	//m_iShowHeight = bs.bmHeight;
	//UpdateData(false);
}
void CChangeBmp::ShowImg(UINT ID, HBITMAP hBmp)
{
	CWnd* pWnd = GetDlgItem(ID);
	CDC* pDC = pWnd->GetDC();
	CRect rect; 
	pWnd->GetClientRect(&rect);
	pDC->FillSolidRect(&rect,RGB(128,128,128));
	pWnd->Invalidate();
	pWnd->UpdateWindow();
	BITMAP bs;
	GetObject(hBmp, sizeof(bs), &bs);
	CDC dc;
	if(dc.CreateCompatibleDC(pDC)) {
		int x0, y0, w, h;
		float rx = (float)bs.bmWidth / rect.right, 
			ry = (float)bs.bmHeight / rect.bottom;
		if (rx >= ry) {
			x0 = 0; w = rect.right;
			h = (int)(bs.bmHeight / rx + 0.5);
			y0 = (rect.bottom - h) / 2;
		}
		else {
			y0 = 0; h = rect.bottom;
			w = (int)(bs.bmWidth / ry + 0.5);
			x0 = (rect.right - w) / 2;
		}
		::SelectObject(dc.GetSafeHdc(), hBmp);
		pDC->SetStretchBltMode(HALFTONE);
		pDC->StretchBlt(x0, y0, w, h, &dc, 0, 0, bs.bmWidth, bs.bmHeight, SRCCOPY);
		SetDlgItemInt(IDC_SHOW_WIDTH, bs.bmWidth);
		SetDlgItemInt(IDC_SHOW_HEIGHT, bs.bmHeight);
	}
}
void CChangeBmp::OnPaint()
{
	CPaintDC dc(this); // device context for painting
	// TODO: 在此处添加消息处理程序代码
	// 不为绘图消息调用 CDialog::OnPaint()
	HBITMAP hBmp = (HBITMAP)LoadImage(NULL, m_BmpPathName, 
			IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | 
			LR_DEFAULTCOLOR | LR_DEFAULTSIZE);
		if (hBmp != NULL) {
			BITMAP bm;
			GetObject(hBmp, sizeof(bm), &bm);
			long cb = bm.bmBitsPixel * bm.bmHeight * bm.bmWidthBytes;
			bm.bmBits = new char[cb];
			GetBitmapBits(hBmp, cb, bm.bmBits);
		    m_FileBitmap.CreateBitmapIndirect(&bm);
		}
		ShowImg(IDC_SHOWBMP,m_FileBitmap);
}

						