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In this image:

I want to find this rectangle with all contents(without those grid's lines)

I think the total of the pixels can help a little like:

img = Import["https://i.sstatic.net/lnd5w.png"];
data = Total[ImageData[ImageRotate[ColorNegate[img]]]];
Show[ImageRotate[img], 
 ListLinePlot[data, PlotRange -> All, PlotStyle -> Red]]

And I have such images:

image2

image3

image4

image5

I have no idea to do this thing. Does anyone have an idea?

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    $\begingroup$ Have you asked this question before? It seems very familiar to me... $\endgroup$
    – Carl Lange
    Commented Dec 28, 2018 at 14:36
  • $\begingroup$ Ah, I was thinking of this and this. Just for context purposes :) $\endgroup$
    – Carl Lange
    Commented Dec 28, 2018 at 14:37
  • $\begingroup$ @CarlLange It's not very similar... $\endgroup$
    – yode
    Commented Dec 28, 2018 at 14:37
  • $\begingroup$ The question isn't but the images are, so I wanted to make sure it wasn't a duplicate somehow. That's all! $\endgroup$
    – Carl Lange
    Commented Dec 28, 2018 at 15:10

2 Answers 2

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Binarization and ComponentMeasurements seems the straightforward solution:

img = Import["https://i.sstatic.net/lnd5w.png"];

Selct all components that are less than half as long as the image:

comp = ComponentMeasurements[MorphologicalBinarize[ColorNegate@img], 
   "BoundingBox", #CaliperLength < Min[ImageDimensions[img]]*0.5 &];

This selects all digits and boxes, but not the grid lines, because they are longer than height/2: 

HighlightImage[img, Rectangle @@@ comp[[All, 2]]]

enter image description here

Then combine the individual bounding boxes to one big bounding box:

HighlightImage[img, 
 Rectangle @@ 
  Transpose[MinMax /@ Transpose[Flatten[comp[[All, 2]], 1]]]]

enter image description here

You might have to adjust binarization and the criteria in ComponentMeasurements, but for me, it worked on all the images you posted on the first try.

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  • $\begingroup$ Sorry for catching a cold to delay response. Your method is very simple to understand. But your method cannot deal with the image5. This is why I want to do it with signal-processing method... $\endgroup$
    – yode
    Commented Jan 3, 2019 at 10:54
  • $\begingroup$ @yode: Sure it can, you just need to adjust the criteria function in ComponentMeasurements. $\endgroup$
    – Niki Estner
    Commented Jan 3, 2019 at 11:13
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This works quite well:

findRegion[img_] := TextRecognize[img, "BoundingBox", RecognitionPrior -> "SparseText"]

HighlightImage[#, findRegion@#] & /@ imgs

As you can see, the result for the first image is not perfect unfortunately, but hopefully this gives you some ideas.

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  • $\begingroup$ Yes, as your try, the Tesseract not very stable.. $\endgroup$
    – yode
    Commented Dec 28, 2018 at 14:40

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