WPF文字呈现不一致 [英] WPF text rendering inconsistencies

问题描述

众所周知，WPF 4.0修复了模糊文字问题。设置 TextOptions.TextFormattingMode = Display 使用像素提示来排列字符，这非常有效地提高了清晰度。

WPF 4.0 notoriously fixed the blurry text issue. Setting TextOptions.TextFormattingMode="Display" uses pixel hints to line up characters, which works really well to improve clarity.

但是，当程序在会话0中作为Windows服务运行时，它不起作用；文本返回到理想渲染，这在小尺寸下是完全不可读的。下面是这两种渲染的比较。

However, it does not work while the program is running as a Windows service in session 0; the text goes back to "Ideal" rendering, which at small sizes is completely unreadable. Below is a comparison of the two renderings.

未作为服务运行：

作为服务运行：

渲染代码：

//rtb is a RenderTargetBitmap
//c is a FormatConvertedBitmap with rtb as it's source
while (displayRunning) {
    if (lcd != null) {
        Dispatcher.Invoke(new ThreadStart(delegate() {

            if (dv == null) {
                dv = new DrawingVisual();
                using (DrawingContext dc = dv.RenderOpen()) {
                    dc.DrawRectangle(Brushes.White, new Pen(), new Rect(0, 0, 256, 64));
                    dc.Close();
                }
            }

            rtb.Render(dv);
            rtb.Render((Visual)Content);

            //bitmap output just for testing
            PngBitmapEncoder e = new PngBitmapEncoder();
            e.Frames.Add(BitmapFrame.Create(c));
            using (FileStream f = File.Open("C:\\test.png", FileMode.Create))
                e.Save(f);

            WriteableBitmap bitmapdata = new WriteableBitmap(c);
            srcdata = new byte[bitmapdata.BackBufferStride * bitmapdata.PixelHeight];
            System.Runtime.InteropServices.Marshal.Copy(bitmapdata.BackBuffer, srcdata, 0, srcdata.Length);

        }));
        try {
            framesender.Send(new PicoLCDFrame(srcdata, lcd.OutputReportLength), lcd);
        } catch (NullReferenceException) { } // device was unplugged
    }
    Thread.Sleep(33);
}

我意识到在将字体作为服务呈现时，没有用于提示的屏幕像素，但是它不应该从要渲染到的位图中获取像素提示吗？我有什么能做的吗？

I realize there are no screen pixels for hints when rendering the fonts as a service, but shouldn't it get the pixel hints from the bitmap it is rendering to? Is there anything I can do about this?

编辑：显然，它 IS 使用像素提示，但是它由于某种原因而抗锯齿。下面是渲染的位图在降采样为1 bits / pxel之前。

Apparently, it IS using pixel hints, but it is anti-aliasing for some reason. Below is the rendered bitmap before it is downsampled to 1 bits/pxel.

我确实设置了 TextOptions.TextRenderingMode = Aliased WPF是作为服务运行时忽略的吗？降采样后，它必须打开才能看起来不错。我该如何强制呢？

I do have TextOptions.TextRenderingMode="Aliased" set and it seems that WPF is ignoring that when running as a service? It needs to be on to look good when downsampled. How can I force it?

EDIT2：可能与以0级（软件模式）运行的WPF渲染有关服务和方法2（硬件），而不是方法。

It may have something to do with WPF rendering in Tier 0 (software mode) when running as a service and Tier 2 (hardware) when not.

EDIT3：在Windows XP上，作为服务，它呈现如下：

On Windows XP, as a service, it renders like this:

请注意边距差异，字体大小差异以及其他完美的呈现方式。是WTF吗？

Notice the margin difference, the font size difference, and an otherwise perfect rendering. WTF?

推荐答案

Windows服务中的UserInterface代码不是一个好主意，因为它是不受支持的方案。 GDI +（System.Drawing。*）存在相同的限制，WPF也具有相同的限制。

UserInterface code in windows service is not a good idea its an unsupported scenario. The same limitation was there with GDI+ (System.Drawing.*) and same limitation applies to WPF also.

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