无法使用GDI（MFC）实现DIB打印 [英] Unable to implement DIB printing with GDI (MFC)
问题描述
MFC doc /视图体系结构，GDI绘图/打印。我有一个DIB后台缓冲区，我需要显示和打印。
经过漫长而痛苦的道路，我得出结论，我需要使用DIB创建与CreateDIBSection DDB使用CreateCompatibleBitmap创建），我必须使用StretchDIBits（而不是StretchBlt）将它转换到打印机直流。
但我无法让这个东西工作。
这是我所做的：
在我的初始化例程中，我设置了backbuffer，
//准备设备上下文：
CClientDC aDC
OnPrepareDC（& aDC）;
//设置适当的backbuffer：
_pMemDc = new CDC;
_pMemDc-> CreateCompatibleDC（& aDC）;
memset（& _bitmapInfo，0，sizeof（BITMAPINFO））;
_bitmapInfo.bmiHeader.biSize = sizeof（BITMAPINFOHEADER）;
_bitmapInfo.bmiHeader.biWidth = _sizeBackBuffer.cx;
_bitmapInfo.bmiHeader.biHeight = -_sizeBackBuffer.cy; // top-down
_bitmapInfo.bmiHeader.biPlanes = 1;
_bitmapInfo.bmiHeader.biBitCount = 24; // Maybe 32？
_bitmapInfo.bmiHeader.biCompression = BI_RGB;
HANDLE hMemBitmap = CreateDIBSection（aDC.GetSafeHdc（），& _bitmapInfo，DIB_RGB_COLORS，（void **）& _pBitmapRawBits，0，0）;
_hOldSelBitmap =（HBITMAP）_pMemDc-> SelectObject（hMemBitmap）;
带下划线的变量是（私有）成员变量，声明如下：
CDC * _pMemDc; // Backbuffer memory dc
HBITMAP _hOldSelBitmap;
BITMAPINFO _bitmapInfo; // Backbuffer DIB（header-only）
unsigned char * _pBitmapRawBits; //指向DIB的像素数据的指针
SIZE _sizeBackBuffer; // Backbuffer的大小，即DIB的大小
现在下面是我在OnDraw覆盖：
首先，我得到这样绘制的区域（简化代码）：
code> CRect rectClipBoxPlayground;
if（pDC-> IsPrinting（））
{
rectClipBoxPlayground = _printingParams.pPrintInfo-> m_rectDraw;
}
else
{
pDC-> GetClipBox（& rectClipBoxPlayground）;
}
然后我计算我的backbuffer中的对应的rect坐标， ）大于DC。此计算的细节在这里不相关，我只是说
CRect rectClipBoxBackBuffer;
表示backbuffer的相应rect（在backbuffer的像素坐标中）。
然后我绘制到我的后台缓冲区，使用_pMemDc内存dc。
最后是我遇到的麻烦的部分：目标dc（屏幕或打印机）。这是我做的：
//将缓冲区复制到屏幕/打印机dc：
pDC - > SetStretchBltMode（HALFTONE）;
SetBrushOrgEx（pDC-> GetSafeHdc（），0，0，0）;
//下面的StretchBlt工程的指定代码（！）INSTEAD OF StretchDIBits。
//
// BOOL bSuccess = pDC-> StretchBlt（rectClipBoxPlayground.left，rectClipBoxPlayground.top，
// rectClipBoxPlayground.Width（），rectClipBoxPlayground.Height（），
// _pMemDc，rectClipBoxBackBuffer.left，rectClipBoxBackBuffer.top，
// rectClipBoxBackBuffer.Width（），rectClipBoxBackBuffer.Height（），SRCCOPY）;
HBITMAP hMemBitmap =（HBITMAP）_pMemDc-> SelectObject（_hOldSelBitmap）;
DWORD dwLines = StretchDIBits（pDC-> GetSafeHdc（），
rectClipBoxPlayground.left，rectClipBoxPlayground.top，rectClipBoxPlayground.Width（），rectClipBoxPlayground.Height（），
rectClipBoxBackBuffer .left，rectClipBoxBackBuffer.top，rectClipBoxBackBuffer.Width（），rectClipBoxBackBuffer.Height（），
_pBitmapRawBits，& _bitmapInfo，DIB_RGB_COLORS，SRCCOPY）;
_pMemDc-> SelectObject（hMemBitmap）;问题是，StretchBlt的注释掉的代码工作正常（除了在某些打印机上打印），然而，但我不能使用它，因为一些打印机有麻烦。所以我不得不使用StretchDIBits。请注意，我首先从其内存dc暂时取消选择DIB，以便它不与任何直流相关联。然后我使用StretchDIBits但事情只是不工作！输出乱七八糟，像我给不正确的坐标，区域绘制偏移从他们应该绘制的地方，有时完全黑色。所以我必须缺少一些东西（也许是非常微不足道的）。帮帮我！我尝试改变rectClipBoxBackBuffer.top和bitmapInfo.bmiHeader.biHeight的符号，结果改变，但没有什么工作原理。
我做错了什么？
解决方案关于StretchDIBits的Microsoft文档是完全错误的。我发现Y轴的方向必须改变。现在下面的代码工作：
//将缓冲区复制到屏幕dc：
pDC-> SetStretchBltMode（HALFTONE）;
SetBrushOrgEx（pDC-> GetSafeHdc（），0，0，0）;
HBITMAP hMemBitmap =（HBITMAP）_pMemDc-> SelectObject（_hOldSelBitmap）;
DWORD dwLines = StretchDIBits（pDC-> GetSafeHdc（），
rectClipBoxPlayground.left，rectClipBoxPlayground.top，rectClipBoxPlayground.Width（），rectClipBoxPlayground.Height（），
rectClipBoxBackBuffer .left，_sizeBackBuffer.cy - rectClipBoxBackBuffer.top - rectClipBoxBackBuffer.Height（），rectClipBoxBackBuffer.Width（），rectClipBoxBackBuffer.Height（），
_pBitmapRawBits，& _bitmapInfo，DIB_RGB_COLORS，SRCCOPY）;
_pMemDc-> SelectObject（hMemBitmap）;
PS：现在它适用于屏幕绘图和打印预览，但实际打印失败，原始问题：如何在打印机上打印DIB backbuffer - GDI，MFC
MFC doc/view architecture, GDI drawing/printing. I have a DIB backbuffer I need to display and print.
After the long and painful road I came to the conclusion than I need to use DIB created with CreateDIBSection (rather than DDB created with CreateCompatibleBitmap), and I have to blit it onto printer dc with StretchDIBits (rather than StretchBlt).
But i'm not able to get this thing to work.
Here is what I do:
In my initialization routine, I setup the backbuffer, like this:
// Prepare device context:
CClientDC aDC(this);
OnPrepareDC(&aDC);
// Setup proper backbuffer:
_pMemDc = new CDC;
_pMemDc->CreateCompatibleDC(&aDC);
memset(&_bitmapInfo, 0, sizeof(BITMAPINFO));
_bitmapInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
_bitmapInfo.bmiHeader.biWidth = _sizeBackBuffer.cx;
_bitmapInfo.bmiHeader.biHeight = -_sizeBackBuffer.cy; // top-down
_bitmapInfo.bmiHeader.biPlanes = 1;
_bitmapInfo.bmiHeader.biBitCount = 24; // Maybe 32?
_bitmapInfo.bmiHeader.biCompression = BI_RGB;
HANDLE hMemBitmap = CreateDIBSection(aDC.GetSafeHdc(), &_bitmapInfo, DIB_RGB_COLORS, (void**)&_pBitmapRawBits, 0, 0);
_hOldSelBitmap = (HBITMAP)_pMemDc->SelectObject(hMemBitmap);
Variables with underscores are (private) member variables, declared like this:
CDC *_pMemDc; // Backbuffer memory dc
HBITMAP _hOldSelBitmap;
BITMAPINFO _bitmapInfo; // Backbuffer DIB (header-only)
unsigned char *_pBitmapRawBits; // Pointer to pixel data of DIB
SIZE _sizeBackBuffer; // Size of backbuffer, i.e. size of that DIB
Now below is what I do in my OnDraw override:
Firstly I get the area to be drawn like this (simplified code):
CRect rectClipBoxPlayground;
if (pDC->IsPrinting())
{
rectClipBoxPlayground = _printingParams.pPrintInfo->m_rectDraw;
}
else
{
pDC->GetClipBox(&rectClipBoxPlayground);
}
Then I calculate the corresponding rect coordinates in my backbuffer, which is usually (much) larger than the DC. Details of this calculation are irrelevant here, I just say that
CRect rectClipBoxBackBuffer;
represents the corresponding rect of backbuffer (in pixel coordinates of backbuffer).
Then I draw onto my backbuffer, using the _pMemDc memory dc.
And finally comes the part where I have troubles: blitting my DIB onto target dc (screen or printer). Here is what I do:
// Copy back buffer to screen/printer dc:
pDC->SetStretchBltMode(HALFTONE);
SetBrushOrgEx(pDC->GetSafeHdc(), 0, 0, 0);
// BELOW COMMENTED CODE OF StretchBlt WORKS(!) INSTEAD OF StretchDIBits.
//
//BOOL bSuccess = pDC->StretchBlt(rectClipBoxPlayground.left, rectClipBoxPlayground.top,
// rectClipBoxPlayground.Width(), rectClipBoxPlayground.Height(),
// _pMemDc, rectClipBoxBackBuffer.left, rectClipBoxBackBuffer.top,
// rectClipBoxBackBuffer.Width(), rectClipBoxBackBuffer.Height(), SRCCOPY);
HBITMAP hMemBitmap = (HBITMAP)_pMemDc->SelectObject(_hOldSelBitmap);
DWORD dwLines = StretchDIBits(pDC->GetSafeHdc(),
rectClipBoxPlayground.left, rectClipBoxPlayground.top, rectClipBoxPlayground.Width(), rectClipBoxPlayground.Height(),
rectClipBoxBackBuffer.left, rectClipBoxBackBuffer.top, rectClipBoxBackBuffer.Width(), rectClipBoxBackBuffer.Height(),
_pBitmapRawBits, &_bitmapInfo, DIB_RGB_COLORS, SRCCOPY);
_pMemDc->SelectObject(hMemBitmap);
The problem is, the commented-out code of StretchBlt works flawlessly (except printing on some printers), but I can't use it because some printers have troubles with it. So I have to use StretchDIBits. Note that I firstly unselect the DIB from its memory dc temporarily, so that it is not associated with any dc. Then I use StretchDIBits but things just don't work! Output is messed up, like I give incorrect coordinates, areas are drawn off-set from where they should be drawn, and sometimes totally black. So I must be missing something (maybe something very trivial). Help! I tried changing signs of rectClipBoxBackBuffer.top and bitmapInfo.bmiHeader.biHeight, the results change, but nothing works like it should.
What am I doing wrong??
解决方案 Microsoft's documentation about StretchDIBits is totally wrong. I found out that direction of Y axis has to be changed. Now following code works:
// Copy back buffer to screen dc:
pDC->SetStretchBltMode(HALFTONE);
SetBrushOrgEx(pDC->GetSafeHdc(), 0, 0, 0);
HBITMAP hMemBitmap = (HBITMAP)_pMemDc->SelectObject(_hOldSelBitmap);
DWORD dwLines = StretchDIBits(pDC->GetSafeHdc(),
rectClipBoxPlayground.left, rectClipBoxPlayground.top, rectClipBoxPlayground.Width(), rectClipBoxPlayground.Height(),
rectClipBoxBackBuffer.left, _sizeBackBuffer.cy - rectClipBoxBackBuffer.top - rectClipBoxBackBuffer.Height(), rectClipBoxBackBuffer.Width(), rectClipBoxBackBuffer.Height(),
_pBitmapRawBits, &_bitmapInfo, DIB_RGB_COLORS, SRCCOPY);
_pMemDc->SelectObject(hMemBitmap);
P.S.: Now it works for screen drawing and print preview, but fails for actual printing, which was my original problem discussed here: How to print DIB backbuffer on printer - GDI, MFC
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