区分低对比度和高对比度的文本图像 [英] Differentiating low and high contrast text images

问题描述

Hello everyone,
I am a student just started with one image processing project.
I am working on OCR and want to reject/handle images based on low and high contrast separately. 
Currently I am working on differentiating low and high contrast text images. 
These images are of metallic plates and having various of noises, few samples are attached below.
<a href="https://drive.google.com/open?id=0B81c7NmWqSF9OEE3MWNLZ0haQ2s">1.jpg - Google Drive</a>[<a href="https://drive.google.com/open?id=0B81c7NmWqSF9OEE3MWNLZ0haQ2s" target="_blank" title="New Window">^</a>]

<a href="https://drive.google.com/open?id=0B81c7NmWqSF9UGFYTW0wRUNQM2c">3.jpg - Google Drive</a>[<a href="https://drive.google.com/open?id=0B81c7NmWqSF9UGFYTW0wRUNQM2c" target="_blank" title="New Window">^</a>]

<a href="https://drive.google.com/open?id=0B81c7NmWqSF9enB4NzVKTkJWZU0">4.jpg - Google Drive</a>[<a href="https://drive.google.com/open?id=0B81c7NmWqSF9enB4NzVKTkJWZU0" target="_blank" title="New Window">^</a>]

<a href="https://drive.google.com/open?id=0B81c7NmWqSF9OGgwVFR2LXJEZG8">2.jpg - Google Drive</a>[<a href="https://drive.google.com/open?id=0B81c7NmWqSF9OGgwVFR2LXJEZG8" target="_blank" title="New Window">^</a>]

Can anyone suggest a way/parameter to differentiate theses images?

Thank you in advance for your valuable time.

我尝试过：



图片有所不同解析度。

尝试累积直方图但失败了。

What I have tried:

Images are of varying resolution.
Tried cumulative histogram but failed.

推荐答案

与图像识别中的许多其他东西不同，对比度的测量可以是客观的;总是可以解决并且容易获得。你可以从这里开始：

对比（愿景） - 维基百科，免费的百科全书 ，

显示对比 - 维基百科，免费的百科全书。



当然，你不能使用操作功能和背景（韦伯）概念的测量，因为图像不包含任何预知信息，如何从背景中识别特征。 />


现在，我不太确定你是否必须应用对比度测量来区分输入图像并拒绝它们。在某些情况下，需要这种方法。只有一件事：在图像识别之前需要应用的图像变换之一是提高图像对比度;经常（也许并不总是），你需要把它提升到极端。这取决于具体问题。

-SA

Unlike many other things in image recognition, the measures of contrast can be objective; always solvable and easy to obtain. You can start here:
Contrast (vision) — Wikipedia, the free encyclopedia,
Display contrast — Wikipedia, the free encyclopedia.

Of course, you cannot use the measure operating the concepts of "feature" and "background" (Weber), because an image does not contain any predefined information of how to tell feature from background.

Now, I'm not quite sure that you have to apply the contrast measure to discriminate input images and rejecting them. In some cases, this approach is needed. Just one thing: one of the image transforms needed to apply before image recognition is boosting the image contrast; often (perhaps not always), you need to boost it to extremes. It depends on particular problem.

—SA

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