Autovue_Drawing Compare 2

[DesEngineer4]

Hello,

Is there any open source software like Autovue to compare engineering drawings? The comparison result should show in colors what is deleted and what is added. Please suggest.

Thanks & Regards

 

[3DDave]

I used Photoshop Elements - Start with a full black layer, then read in the older drawing PDF/png/jpeg/bmp to a new layer and use a modification layer of Red; read in the newer drawing PDF/png/jpeg/bmp to a new layer and add a modification layer of 50% transparent green.

Everywhere they match, the color will be an unpleasant yellow/brown. Where only the old remains is red. Where only the new appears will be green.

You can use "select by color" to find even a single pixel of red or green, allowing easy location of so small a change as a "." becoming a ",". Ordinary Photoshop tools can be used if there is a change of line width to select and either enlarge or trim pixel widths.

Unlike most compare software if someone moved a view, even to a to a new sheet, you can make the same adjustment to the pixels of whichever layer you like to confirm the actual changes to the view contents.

Also unlike most compare software, it can handle unskewing scans, fixing different X/Y scaling from scanning, and make a fairly good comparison to hand-drawn modifications.

Text may be tedious; not sure that most compare software can handle changes in line breaks, but copy/paste in Photoshop Elements could manage it.

Best, a single file can handle multiple versions so a single drawing full revision status can be retained and any pair of versions compared by changing the color/transparency and showing only the desired layers, allowing the full history to be examined in one location.

This can also be done in the free GIMP software, though I liked the Photoshop workflow better.

 

[DesEngineer4]

Hi Dave,

Thank you for detailed explanation, photshop is working good in my personal computer but unable to install in my office PC due to IT restrictions. Is there anyway to simply create a small software or tool only for this purpose?

Thanks & Regards

 

[3DDave]

How would some other avoid IT restrictions? It would still be almost as complex as photoshop but not be from a more-or-less trusted software supplier. If the problem is price, GIMP is free and Photoshop elements is a 1 time US$100 purchase, no subscription.

 

[DesEngineer4]

Hi Dave,
Somehow convinced them for GIMP in our official system, they will install in couple of days. Can we achieve the similar comparison outcome from GIMP?

Thanks & Regards

 

[3DDave]

For GIMP

Open the first - note that for pdf you can set the pixel density, 100 dpi should be enough.
Menu "Select" "By Color" and pick the white area of the new layer and then Cut to remove all the white background.
"Select" "Invert" to select all the mark/line/text pixels.
Change the foreground color to Red
Menu "Edit" "Fill with FG Color"
Set the layer opacity to 60-70% (slider on the layer tool tab)

Open the second - if it is the same size pdf use the same pixel density as before - the goal is to get a matching of pixels without scaling to minimize "grey" pixels from antialiasing.
Menu "Select" "By Color" and pick the white area of the new layer and then Cut to remove all the white background.
"Select" "Invert" to select all the mark/line/text pixels.
Change the foreground color to Green
Menu "Edit" "Fill with FG Color"
Go back to the first and paste
Shift the image as necessary to gain the best alignment between the old and new. One must use the mouse pointer at least once on a visible pixel in the floating layer to move it, then one can use the arrow keys for small motions.
Then right click the "floating selection" and select "To New Layer"
Set the layer opacity to 40% (slider on the layer tool tab)

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Optional change the FG color to Red and BG color to Green and, for the second layer, "Fill with BG" color
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Unlike Photoshop, GIMP does not seem happy at selecting combined colors from multiple layers. One can see the separate colors, but GIMP doesn't, so to select for small areas by color one needs to menu "Layer" "Merge down" which is unfortunate, but if one "duplicates the layers first they can be preserved.

 

[3DDave]

I forgot a step - creating the black background layer is very helpful in distinguishing the overlaid colors.