将PDF转换为高分辨率图像

本文翻译自：Convert PDF to image with high resolution

I'm trying to use the command line program convert to take a PDF into an image (JPEG or PNG). 我正在尝试使用命令行程序convert PDF转换为图像（JPEG或PNG）。 Here is one of the PDFs that I'm trying to convert. 这是我要转换的PDF之一 。

I want the program to trim off the excess white-space and return a high enough quality image that the superscripts can be read with ease. 我希望程序修剪掉多余的空白并返回足够高质量的图像，以便可以轻松读取上标。

This is my current best attempt . 这是我目前的最佳尝试 。 As you can see, the trimming works fine, I just need to sharpen up the resolution quite a bit. 如您所见，修整效果很好，我只需要稍微提高一下分辨率即可。 This is the command I'm using: 这是我正在使用的命令：

convert -trim 24.pdf -resize 500% -quality 100 -sharpen 0x1.0 24-11.jpg

I've tried to make the following conscious decisions: 我尝试做出以下有意识的决定：

• resize it larger (has no effect on the resolution) 调整它的大小（对分辨率没有影响）
• make the quality as high as possible 使质量尽可能高
• use the -sharpen (I've tried a range of values) 使用-sharpen （我尝试了一系列值）

Any suggestions please on getting the resolution of the image in the final PNG/JPEG higher would be greatly appreciated! 任何关于在最终的PNG / JPEG中获得更高图像分辨率的建议，将不胜感激！

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#1楼

参考：https://stackoom.com/question/RiGM/将PDF转换为高分辨率图像

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#2楼

它还可以为您带来良好的效果：

exec("convert -geometry 1600x1600 -density 200x200 -quality 100 test.pdf test_image.jpg");

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#3楼

Personally I like this. 我个人喜欢这样。

convert -density 300 -trim test.pdf -quality 100 test.jpg

It's a little over twice the file size, but it looks better to me. 它是文件大小的两倍多，但对我来说看起来更好。

-density 300 sets the dpi that the PDF is rendered at. -density 300设置渲染PDF的dpi。

-trim removes any edge pixels that are the same color as the corner pixels. -trim删除与角像素颜色相同的所有边缘像素。

-quality 100 sets the JPEG compression quality to the highest quality. -quality 100将JPEG压缩质量设置为最高质量。

Things like -sharpen don't work well with text because they undo things your font rendering system did to make it more legible. -sharpen之类的东西不能很好地与文本配合使用，因为它们会撤消字体渲染系统所做的使它更清晰的事情。

If you actually want it blown up use resize here and possibly a larger dpi value of something like targetDPI * scalingFactor That will render the PDF at the resolution/size you intend. 如果您确实希望将其炸毁，请在此处使用调整大小，并可能使用较大的dpi值，例如targetDPI * scalingFactor ，它将以您想要的分辨率/大小呈现PDF。

Descriptions of the parameters on imagemagick.org are here 在这里 imagemagick.org上的参数说明

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#4楼

I have found it both faster and more stable when batch-processing large PDFs into PNGs and JPGs to use the underlying gs (aka Ghostscript) command that convert uses. 当将大型PDF批量处理为PNG和JPG以使用convert使用的基础gs （又名Ghostscript）命令时，我发现它既更快又更稳定。

You can see the command in the output of convert -verbose and there are a few more tweaks possible there (YMMV) that are difficult / impossible to access directly via convert . 您可以在convert -verbose的输出中看到命令，并且那里还有一些可能的调整（YMMV），很难/不可能直接通过convert访问。

However, it would be harder to do your trimming and sharpening using gs , so, as I said, YMMV! 但是，使用gs修剪和锐化将更加困难，因此，正如我所说的，YMMV！

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#5楼

One more suggestion is that you can use GIMP. 另一个建议是您可以使用GIMP。

Just load the PDF file in GIMP->save as .xcf and then you can do whatever you want to the image. 只需将GIMP-> PDF文件加载为.xcf，然后就可以对图像执行任何操作。

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#6楼

PNG file you attached looks really blurred. 您附加的PNG文件看起来真的很模糊。 In case if you need to use additional post-processing for each image you generated as PDF preview, you will decrease performance of your solution. 如果您需要对作为PDF预览生成的每个图像进行额外的后期处理，则会降低解决方案的性能。

2JPEG can convert PDF file you attached to a nice sharpen JPG and crop empty margins in one call: 2JPEG可以转换您附加到一个不错的JPG的PDF文件，并在一次调用中裁剪空白边距：

2jpeg.exe -src "C:\In\*.*" -dst "C:\Out" -oper Crop method:autocrop