JpegBitmapEn codeR叶在文件末尾灰色条纹？ [英] JpegBitmapEncoder leaves gray streak at end of file?

问题描述

我在尝试做一些简单的图像处理的WPF成像组件工作。我粗略下面就的MS文章如何恩code＆放;德code JPEG图像。

I'm working with the WPF imaging components in an attempt to do some simple image manipulation. I'm roughly following the MS article on How to Encode & Decode a JPEG Image.

我的code是简单的：

My code is simple:

BitmapImage bi = new BitmapImage();

bi.BeginInit();
bi.UriSource = new Uri("D:\\Temp\\StackOverflowCapture.png");
//bi.DecodePixelWidth = 1024;
//bi.DecodePixelHeight = 768;
bi.EndInit();

var jpg                  = new JpegBitmapEncoder();
    jpg.QualityLevel     = 90;
    //jpg.FlipHorizontal = false;
    //jpg.FlipVertical   = false;
    jpg.Frames.Add(BitmapFrame.Create(bi));

var fs = new FileStream("D:\\Temp\\StackOverflow_Result.jpg", FileMode.Create);

jpg.Save( fs );
jpg = null;

在code段创建一个奇怪的神器，其中最后几个行是纯灰色的块。这几乎就像如果EN codeR刚跑出像素写的。灰色的量2倍或3x视我为输入（各项决议，JPEG，PNG）或选择启用（强制在德code分辨率）使用的图像上的因素而变化。最终的效果是一样的，但是，你可以从下面的图片中看到的。

The code snippet creates an odd artifact, where the last few "lines" are a block of solid gray. It's almost as if the encoder just ran out of pixels to write. The amount of gray varies by a factor of 2x or 3x depending on the image I use as input (various resolutions, jpeg, png) or the options I enable (forcing resolution on decode). The net effect is the same, however, as you can see from the images below.

我的源图像是：

输出图像（注意在底部的灰色带）：

Output image ( note the gray band at the bottom):

这是怎么回事？我如何得到一个干净的转换？

What's going on here? How do I get a clean convert?

推荐答案

这肯定是两耳之间的短路。对于其他有类似弱点的缘故，不过，我回答我的问题。

This was definitely a short circuit between the ears. For the sake of others with similar frailties, however, I'm answering my own question.

您需要关闭/刷新流。另外，这将是很好的做法，在创建 FS A 使用块。

You need to close/flush the stream. Alternately, it would be good practice to create fs in a using block.

修改code是这样的：

Modified code is thus:

BitmapImage bi = new BitmapImage();

bi.BeginInit();
bi.UriSource = new Uri("D:\\Temp\\StackOverflow_Source.png");
bi.EndInit();

var jpg                  = new JpegBitmapEncoder();
    jpg.QualityLevel     = 90;
    jpg.Frames.Add(BitmapFrame.Create(bi));

var fs = new FileStream("D:\\Temp\\StackOverflow_Result.jpg", FileMode.Create);

jpg.Save( fs );
fs.close();       <--- duh, flush the stream to disk
jpg = null;

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