我正在使用C++
和pure WinApi
创建桌面应用程序。我需要显示作为SVG
给我的图像。
由于WinAPI
仅支持EMF
个文件作为矢量格式,因此我使用Inkscape
将文件转换为EMF
。我的图形设计技能处于初级水平,但我已成功将SVG
文件转换为EMF
。然而,结果并不像原始的那样,它可以说不那么“精确”。
如果我将SVG
导出为PNG
并将其显示为GDI+
,则结果与原始文件相同。不幸的是我需要矢量格式。
要确切了解我的意思,请下载SVG
以及EMF
和PNG
我制作的here。只需点击下载:test.rar 以上5颗黄星(见下图)。
以下是创建重现问题的最小应用程序的说明:
1)在Win32 project
中创建默认Visual Studio
(我使用VS 2008,但这不应该是问题);
2)像这样重写WM_PAINT
:
case WM_PAINT:
{
hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code here...
RECT rcClient;
GetClientRect( hWnd, &rcClient );
FillRect( hdc, &rcClient, (HBRUSH)GetStockObject( LTGRAY_BRUSH) );
// put metafile in the same place your app is
HENHMETAFILE hemf = GetEnhMetaFile( L".\\test.emf" );
ENHMETAHEADER emh;
GetEnhMetaFileHeader( hemf, sizeof(emh), &emh );
// rescale metafile, and keep proportion
UINT o_height = emh.rclFrame.bottom - emh.rclFrame.top,
o_width = emh.rclFrame.right - emh.rclFrame.left;
float scale = 0.5;
scale = (float)( rcClient.right - rcClient.left ) / o_width;
if( (float)( rcClient.bottom - rcClient.top ) / o_height < scale )
scale = (float)( rcClient.bottom - rcClient.top ) / o_height;
int marginX = ( rcClient.right - rcClient.left ) - (int)( o_width * scale );
int marginY = ( rcClient.bottom - rcClient.top ) - (int)( o_height * scale );
marginX /= 2;
marginY /= 2;
rcClient.left = rcClient.left + marginX;
rcClient.right = rcClient.right - marginX;
rcClient.top = rcClient.top + marginY;
rcClient.bottom = rcClient.bottom - marginY;
// Draw the picture.
PlayEnhMetaFile( hdc, hemf, &rcClient );
// Release the metafile handle.
DeleteEnhMetaFile(hemf);
EndPaint(hWnd, &ps);
}
break;
3)在WM_SIZE
下面的WM_ERASEBKGND
和WM_PAINT
添加以下处理程序:
case WM_SIZE:
InvalidateRect( hWnd, NULL, FALSE );
return 0L;
case WM_ERASEBKGND:
return 1L;
4)将窗口调整到尽可能小的尺寸,然后将其最大化。
请注意,窗口越大,图像质量越好,但图像得到的“精确度越低”越小。我在Windows XP
上进行了测试。
我请求您的帮助,以获得与原始SVG
相同的EMF文件图形质量。
感谢您的时间和精力。最好的问候。
答案 0 :(得分:3)
解决了!
如果不是所有我提交的解决方案,解决方案都会提供很多。因此,我决定用这个替换它。
需要考虑许多事项,并采用一些概念来获得理想的结果。这些包括(没有特别的顺序)
我还注意到,每次刷新屏幕时,我都会使用旧代码手动绘制背景。一个更好的方法是创建一个patternBrush,然后使用FillRect函数简单地复制。这比用纯色填充矩形然后在顶部绘制线要快得多。我可能不愿意重新编写代码的这一部分,但我会在其他项目中包含一个参考片段供我参考。
以下是我从以下代码中获得的结果的几张照片:
这是我用来实现它的代码:
#define WINVER 0x0500 // for alphablend stuff
#include <windows.h>
#include <commctrl.h>
#include <stdio.h>
#include <stdint.h>
#include "resource.h"
HINSTANCE hInst;
HBITMAP mCreateDibSection(HDC hdc, int width, int height, int bitCount)
{
BITMAPINFO bi;
ZeroMemory(&bi, sizeof(bi));
bi.bmiHeader.biSize = sizeof(bi.bmiHeader);
bi.bmiHeader.biWidth = width;
bi.bmiHeader.biHeight = height;
bi.bmiHeader.biPlanes = 1;
bi.bmiHeader.biBitCount = bitCount;
bi.bmiHeader.biCompression = BI_RGB;
return CreateDIBSection(hdc, &bi, DIB_RGB_COLORS, 0,0,0);
}
void makePixelsTransparent(HBITMAP bmp, byte r, byte g, byte b)
{
BITMAP bm;
GetObject(bmp, sizeof(bm), &bm);
int x, y;
for (y=0; y<bm.bmHeight; y++)
{
uint8_t *curRow = (uint8_t *)bm.bmBits;
curRow += y * bm.bmWidthBytes;
for (x=0; x<bm.bmWidth; x++)
{
if ((curRow[x*4 + 0] == b) && (curRow[x*4 + 1] == g) && (curRow[x*4 + 2] == r))
{
curRow[x*4 + 0] = 0; // blue
curRow[x*4 + 1] = 0; // green
curRow[x*4 + 2] = 0; // red
curRow[x*4 + 3] = 0; // alpha
}
else
curRow[x*4 + 3] = 255; // alpha
}
}
}
// Note: maskCol should be as close to the colour of the background as is practical
// this is because the pixels that border transparent/opaque areas will have
// their colours derived from a blending of the image colour and the maskColour
//
// I.e - if drawing to a white background (255,255,255), you should NOT use a mask of magenta (255,0,255)
// this would result in a magenta-ish border
HBITMAP HbitmapFromEmf(HENHMETAFILE hEmf, int width, int height, COLORREF maskCol)
{
ENHMETAHEADER emh;
GetEnhMetaFileHeader(hEmf, sizeof(emh), &emh);
int emfWidth, emfHeight;
emfWidth = emh.rclFrame.right - emh.rclFrame.left;
emfHeight = emh.rclFrame.bottom - emh.rclFrame.top;
// these are arbitrary and selected to give a good mix of speed and accuracy
// it may be worth considering passing this value in as a parameter to allow
// fine-tuning
emfWidth /= 8;
emfHeight /= 8;
// draw at 'native' size
HBITMAP emfSrcBmp = mCreateDibSection(NULL, emfWidth, emfHeight, 32);
HDC srcDC = CreateCompatibleDC(NULL);
HBITMAP oldSrcBmp = (HBITMAP)SelectObject(srcDC, emfSrcBmp);
RECT tmpEmfRect, emfRect;
SetRect(&tmpEmfRect, 0,0,emfWidth,emfHeight);
// fill background with mask colour
HBRUSH bkgBrush = CreateSolidBrush(maskCol);
FillRect(srcDC, &tmpEmfRect, bkgBrush);
DeleteObject(bkgBrush);
// draw emf
PlayEnhMetaFile(srcDC, hEmf, &tmpEmfRect);
HDC dstDC = CreateCompatibleDC(NULL);
HBITMAP oldDstBmp;
HBITMAP result;
result = mCreateDibSection(NULL, width, height, 32);
oldDstBmp = (HBITMAP)SelectObject(dstDC, result);
SetStretchBltMode(dstDC, HALFTONE);
StretchBlt(dstDC, 0,0,width,height, srcDC, 0,0, emfWidth,emfHeight, SRCCOPY);
SelectObject(srcDC, oldSrcBmp);
DeleteDC(srcDC);
DeleteObject(emfSrcBmp);
SelectObject(dstDC, oldDstBmp);
DeleteDC(dstDC);
makePixelsTransparent(result, GetRValue(maskCol),GetGValue(maskCol),GetBValue(maskCol));
return result;
}
int rectWidth(RECT &r)
{
return r.right - r.left;
}
int rectHeight(RECT &r)
{
return r.bottom - r.top;
}
void onPaintEmf(HWND hwnd, HENHMETAFILE srcEmf)
{
PAINTSTRUCT ps;
RECT mRect, drawRect;
HDC hdc;
double scaleWidth, scaleHeight, scale;
int spareWidth, spareHeight;
int emfWidth, emfHeight;
ENHMETAHEADER emh;
GetClientRect( hwnd, &mRect );
hdc = BeginPaint(hwnd, &ps);
// calculate the draw-size - retain aspect-ratio.
GetEnhMetaFileHeader(srcEmf, sizeof(emh), &emh );
emfWidth = emh.rclFrame.right - emh.rclFrame.left;
emfHeight = emh.rclFrame.bottom - emh.rclFrame.top;
scaleWidth = (double)rectWidth(mRect) / emfWidth;
scaleHeight = (double)rectHeight(mRect) / emfHeight;
scale = min(scaleWidth, scaleHeight);
int drawWidth, drawHeight;
drawWidth = emfWidth * scale;
drawHeight = emfHeight * scale;
spareWidth = rectWidth(mRect) - drawWidth;
spareHeight = rectHeight(mRect) - drawHeight;
drawRect = mRect;
InflateRect(&drawRect, -spareWidth/2, -spareHeight/2);
// create a HBITMAP from the emf and draw it
// **** note that the maskCol matches the background drawn by the below function ****
HBITMAP srcImg = HbitmapFromEmf(srcEmf, drawWidth, drawHeight, RGB(230,230,230) );
HDC memDC;
HBITMAP old;
memDC = CreateCompatibleDC(hdc);
old = (HBITMAP)SelectObject(memDC, srcImg);
byte alpha = 255;
BLENDFUNCTION bf = {AC_SRC_OVER,0,alpha,AC_SRC_ALPHA};
AlphaBlend(hdc, drawRect.left,drawRect.top, drawWidth,drawHeight,
memDC, 0,0,drawWidth,drawHeight, bf);
SelectObject(memDC, old);
DeleteDC(memDC);
DeleteObject(srcImg);
EndPaint(hwnd, &ps);
}
void drawHeader(HDC dst, RECT headerRect)
{
HBRUSH b1;
int i,j;//,headerHeight = (headerRect.bottom - headerRect.top)+1;
b1 = CreateSolidBrush(RGB(230,230,230));
FillRect(dst, &headerRect,b1);
DeleteObject(b1);
HPEN oldPen, curPen;
curPen = CreatePen(PS_SOLID, 1, RGB(216,216,216));
oldPen = (HPEN)SelectObject(dst, curPen);
for (j=headerRect.top;j<headerRect.bottom;j+=10)
{
MoveToEx(dst, headerRect.left, j, NULL);
LineTo(dst, headerRect.right, j);
}
for (i=headerRect.left;i<headerRect.right;i+=10)
{
MoveToEx(dst, i, headerRect.top, NULL);
LineTo(dst, i, headerRect.bottom);
}
SelectObject(dst, oldPen);
DeleteObject(curPen);
MoveToEx(dst, headerRect.left,headerRect.bottom,NULL);
LineTo(dst, headerRect.right,headerRect.bottom);
}
BOOL CALLBACK DlgMain(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
static HENHMETAFILE hemf;
switch(uMsg)
{
case WM_INITDIALOG:
{
hemf = GetEnhMetaFile( "test.emf" );
}
return TRUE;
case WM_PAINT:
onPaintEmf(hwndDlg, hemf);
return 0;
case WM_ERASEBKGND:
{
RECT mRect;
GetClientRect(hwndDlg, &mRect);
drawHeader( (HDC)wParam, mRect);
}
return true;
case WM_SIZE:
InvalidateRect( hwndDlg, NULL, true );
return 0L;
case WM_CLOSE:
{
EndDialog(hwndDlg, 0);
}
return TRUE;
case WM_COMMAND:
{
switch(LOWORD(wParam))
{
}
}
return TRUE;
}
return FALSE;
}
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
hInst=hInstance;
InitCommonControls();
return DialogBox(hInst, MAKEINTRESOURCE(DLG_MAIN), NULL, (DLGPROC)DlgMain);
}
最后,这是一个使用FillRect函数创建patternBrush以填充背景的示例。此方法适用于任何可平铺的背景。
HBRUSH makeCheckerBrush(int squareSize, COLORREF col1, COLORREF col2)
{
HDC memDC, tmpDC = GetDC(NULL);
HBRUSH result, br1, br2;
HBITMAP old, bmp;
RECT rc, r1, r2;
br1 = CreateSolidBrush(col1);
br2 = CreateSolidBrush(col2);
memDC = CreateCompatibleDC(tmpDC);
bmp = CreateCompatibleBitmap(tmpDC, 2*squareSize, 2*squareSize);
old = (HBITMAP)SelectObject(memDC, bmp);
SetRect(&rc, 0,0, squareSize*2, squareSize*2);
FillRect(memDC, &rc, br1);
// top right
SetRect(&r1, squareSize, 0, 2*squareSize, squareSize);
FillRect(memDC, &r1, br2);
// bot left
SetRect(&r2, 0, squareSize, squareSize, 2*squareSize);
FillRect(memDC, &r2, br2);
SelectObject(memDC, old);
DeleteObject(br1);
DeleteObject(br2);
ReleaseDC(0, tmpDC);
DeleteDC(memDC);
result = CreatePatternBrush(bmp);
DeleteObject(bmp);
return result;
}
结果示例,使用:
创建 HBRUSH bkBrush = makeCheckerBrush(8, RGB(153,153,153), RGB(102,102,102));