读C＃中的打印机设备上下文 [英] Reading a Printer Device Context in C#
问题描述
我能够显示和屏幕设备保存到DIB位图，我愿做同样的打印机设备上下文。我可以得到一个非空的位图，但它始终是纯黑色。
I am able to display and save a screen device to DIB bitmap, and I would like to do the same with a printer device context. I can get a non-null bitmap, but it is always solid black.
下面是code，让我来处理屏幕设备上下文。
Here is the code that allows me to handle a screen device context.
//In size variable we shall keep the size of the window.
SIZE size;
//Win32 API functions are imported in classes
//PlatformInvokeGDI32
//PlatformInvokeUSER32
//Get handle of calc.exe window.
IntPtr hwnd = PlatformInvokeUSER32.FindWindow("SciCalc", "Calculator");
//Get window dimensions
PlatformInvokeUSER32.RECT rect;
PlatformInvokeUSER32.GetWindowRect(hwnd, out rect);
size.cx = rect._Right - rect._Left;
size.cy = rect._Bottom - rect._Top;
//Get the device context of Calculator.
IntPtr hDC = PlatformInvokeUSER32.GetDC(hwnd);
//Draw on the Calculator surface.
Graphics CalculatorGraphics = Graphics.FromHdc(hDC);
Color colorRed = Color.FromName("Red");
Pen penRed = new Pen(colorRed);
CalculatorGraphics.DrawEllipse(penRed, 50, 50, 50, 50);
CalculatorGraphics.Save();
//Here we make a compatible device context in memory for screen device context.
IntPtr hMemDC = PlatformInvokeGDI32.CreateCompatibleDC(hDC);
//Create a compatible bitmap of window size and using screen device context.
m_HBitmap = PlatformInvokeGDI32.CreateCompatibleBitmap(hDC, size.cx, size.cy);
//As m_HBitmap is IntPtr we can not check it against null. For this purspose IntPtr.Zero is used.
if (m_HBitmap != IntPtr.Zero)
{
//Here we select the compatible bitmap in memeory device context and keeps the refrence to Old bitmap.
IntPtr hOld = (IntPtr)PlatformInvokeGDI32.SelectObject(hMemDC, m_HBitmap);
//We copy the Bitmap to the memory device context.
PlatformInvokeGDI32.BitBlt(hMemDC, 0, 0, size.cx, size.cy, hDC, 0, 0, PlatformInvokeGDI32.SRCCOPY);
//We select the old bitmap back to the memory device context.
PlatformInvokeGDI32.SelectObject(hMemDC, hOld);
//We delete the memory device context.
PlatformInvokeGDI32.DeleteDC(hMemDC);
//We release the screen device context.
PlatformInvokeUSER32.ReleaseDC(hwnd, hDC);
//Image is created by Image bitmap handle and returned.
return System.Drawing.Image.FromHbitmap(m_HBitmap);
}
//If m_HBitmap is null retunrn null.
return null;
下面是如何，我得到一个打印机设备上下文：
Here is how I get a printer device context:
//In size variable we shall keep the size of the window.
SIZE size;
size.cx = 1000;
size.cy = 1000;
//Get Printer Handle
IntPtr PrinterHandle;
PlatformInvokeGDI32.PRINTER_DEFAULTSW defaults = new PlatformInvokeGDI32.PRINTER_DEFAULTSW();
PlatformInvokeGDI32.OpenPrinterW("Bullzip PDF Printer", out PrinterHandle, defaults);
//Get Printer Device context
IntPtr PrinterHDC = PlatformInvokeGDI32.CreateDCW("", "Bullzip PDF Printer", "", IntPtr.Zero);
//Initialize DocInfo structure.
PlatformInvokeGDI32.DOCINFOW docInfo = new PlatformInvokeGDI32.DOCINFOW();
//Start printing.
PlatformInvokeGDI32.StartDocW(PrinterHDC, ref docInfo);
PlatformInvokeGDI32.StartPage(PrinterHDC);
Graphics graphics = Graphics.FromHdc(PrinterHDC, PrinterHandle);
Color theColor = Color.FromName("Red");
Pen pen = new Pen(theColor);
graphics.DrawRectangle(pen, 50, 50, 50, 50);
graphics.DrawEllipse(pen, 50, 50, 50, 50);
graphics.Save();
//Here we make a compatible device context in memory for screen device context.
IntPtr hMemDC = PlatformInvokeGDI32.CreateCompatibleDC(PrinterHDC);
//Create a compatible bitmap of window size and using screen device context.
m_HBitmap = PlatformInvokeGDI32.CreateCompatibleBitmap(PrinterHDC, size.cx, size.cy);
//As m_HBitmap is IntPtr we can not check it against null. For this purspose IntPtr.Zero is used.
if (m_HBitmap != IntPtr.Zero)
{
//Here we select the compatible bitmap in memeory device context and keeps the refrence to Old bitmap.
IntPtr hOld = (IntPtr)PlatformInvokeGDI32.SelectObject(hMemDC, m_HBitmap);
//We copy the Bitmap to the memory device context.
PlatformInvokeGDI32.BitBlt(hMemDC, 0, 0, size.cx, size.cy, PrinterHDC, 0, 0, PlatformInvokeGDI32.SRCCOPY);
//We select the old bitmap back to the memory device context.
PlatformInvokeGDI32.SelectObject(hMemDC, hOld);
//We delete the memory device context.
PlatformInvokeGDI32.DeleteDC(hMemDC);
//We release the screen device context.
//PlatformInvokeUSER32.ReleaseDC(hwnd, PrinterHDC);
//Image is created by Image bitmap handle and returned.
PlatformInvokeGDI32.EndPage(PrinterHDC);
PlatformInvokeGDI32.EndDoc(PrinterHDC);
PlatformInvokeGDI32.ClosePrinter(PrinterHandle);
pen.Dispose();
graphics.Dispose();
return System.Drawing.Image.FromHbitmap(m_HBitmap);
}
//If m_HBitmap is null retunrn null.
return null;
我如何可以利用打印机设备上下文？
我如何保存打印机设备上下文DIB？
How can I draw on the printer device context? How can I save the printer device context to DIB?
感谢您，
雅
推荐答案
打印机设备上下文是只写的。
Printer device contexts are write-only.
例如，假设您正在打印到PostScript打印机。您创建一个打印机设备上下文，并绘制它的一些文字。打印机设备驱动程序不包含呈现文本的位图。相反，它创建的PostScript序列命令绘制文本和命令发送给打印机。换言之，不存在要被复制位图。
For example, suppose you are printing to a PostScript printer. You create a printer device context and draw some text on it. The printer device driver does not render a bitmap containing your text. Rather, it creates a sequence of PostScript commands to draw the text and sends the commands to the printer. In other words, there is no bitmap to be copied.
什么是你想达到什么目的？
What are you trying to achieve?
这篇关于读C＃中的打印机设备上下文的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
