Detect distance between text lines

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kaliber
Posts: 5
Joined: 2015-11-13T01:29:10-07:00
Authentication code: 1151

Detect distance between text lines

Post by kaliber »

Hello
Hey I was wondering if anyone could help me with this problem.

Basically I have to measure the space between text lines.

Example image: I have to calculate the y-coordinates of the (virtual) red rectangles (right image).
The background is always transparent; the text color is always black (left image).

Image

No matter if two lines character can collapse

For drawing up this text I use the `caption:` feature.

I know that `--debug annotate` can returns some glyph metrics, but this option cannot supply me the values to get the rid.

Thanks in advance!
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fmw42
Posts: 25562
Joined: 2007-07-02T17:14:51-07:00
Authentication code: 1152
Location: Sunnyvale, California, USA

Re: Detect distance between text lines

Post by fmw42 »

Please always provide your ImageMagick version and platform when asking questions on this forum.


You can average your image to one column and threshold. Then convert to txt: format and look for the lengths of the white regions

Input:
Image

Since your image has red in it, I have to first remove your red.

Code: Select all

convert lines.png -fuzz 50% -fill white -opaque red -auto-level -negate -threshold 20% -negate lines1.png
Image

Now, scale to 1 column and threshold to black and white

Code: Select all

convert lines1.png -scale 1x! -auto-level -negate -threshold 0 -negate lines2.png
Image

Now convert to txt: format and analyze the stretches of white, i.e. gray(255) as white vs gray(0) as black

Code: Select all

convert lines2.png txt:

Code: Select all

# ImageMagick pixel enumeration: 1,299,65535,gray
0,0: (65535,65535,65535)  #FFFFFF  gray(255)
0,1: (65535,65535,65535)  #FFFFFF  gray(255)
0,2: (65535,65535,65535)  #FFFFFF  gray(255)
0,3: (65535,65535,65535)  #FFFFFF  gray(255)
0,4: (65535,65535,65535)  #FFFFFF  gray(255)
0,5: (65535,65535,65535)  #FFFFFF  gray(255)
0,6: (65535,65535,65535)  #FFFFFF  gray(255)
0,7: (65535,65535,65535)  #FFFFFF  gray(255)
0,8: (65535,65535,65535)  #FFFFFF  gray(255)
0,9: (65535,65535,65535)  #FFFFFF  gray(255)
0,10: (65535,65535,65535)  #FFFFFF  gray(255)
0,11: (65535,65535,65535)  #FFFFFF  gray(255)
0,12: (65535,65535,65535)  #FFFFFF  gray(255)
0,13: (65535,65535,65535)  #FFFFFF  gray(255)
0,14: (65535,65535,65535)  #FFFFFF  gray(255)
0,15: (65535,65535,65535)  #FFFFFF  gray(255)
0,16: (65535,65535,65535)  #FFFFFF  gray(255)
0,17: (65535,65535,65535)  #FFFFFF  gray(255)
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0,281: (65535,65535,65535)  #FFFFFF  gray(255)
0,282: (65535,65535,65535)  #FFFFFF  gray(255)
0,283: (65535,65535,65535)  #FFFFFF  gray(255)
0,284: (65535,65535,65535)  #FFFFFF  gray(255)
0,285: (65535,65535,65535)  #FFFFFF  gray(255)
0,286: (65535,65535,65535)  #FFFFFF  gray(255)
0,287: (65535,65535,65535)  #FFFFFF  gray(255)
0,288: (65535,65535,65535)  #FFFFFF  gray(255)
0,289: (65535,65535,65535)  #FFFFFF  gray(255)
0,290: (65535,65535,65535)  #FFFFFF  gray(255)
0,291: (65535,65535,65535)  #FFFFFF  gray(255)
0,292: (65535,65535,65535)  #FFFFFF  gray(255)
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0,298: (65535,65535,65535)  #FFFFFF  gray(255)
You will have to do some scripting to get the heights of the white gaps.
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kaliber
Posts: 5
Joined: 2015-11-13T01:29:10-07:00
Authentication code: 1151

Re: Detect distance between text lines

Post by kaliber »

Thank you very much it. Scaling to 1x solves my headaches.

Great :)
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