About Comparing Drawing PDFs for differences

[dschenken]

I have made good use of Photoshop and Photoshop elements and GIMP for drawing comparisons. They can import most raster formats and interpret PDF for conversion to raster.

Because the comparison is done with a raster image, the image parts can be moved, rescaled, deskewed, despeckled, or thickened or thinned to account for differences between the versions. For example, a typical drawing change is to move a view from one sheet to another; this is something typical comparison software cannot deal with. In addition, differences can be visibly amplified so the user doesn't need extraordinary care to spot them.

The comparison result is easily saved in any number of low level formats (.gif, .png), so that a third party can verify the check was done using almost any imaging tool (even a web browser) and, because Photoshop/GIMP is a drawing program, annotations can be made - text and graphics highlighting any changes. Since Photoshop and GIMP are layer based, a single file can retain comparisons for any number of versions, if desired.

I tried messaging, but that doesn't work now. And I'm not under maint, so I can't comment on or vote for ideas.

Drawing Change Checking

Using Photoshop or GIMP to find and emphasize differences between versions of images - drawing sheets for example.

Basic steps
1) Take original image and convert to a layer
2) Fill the markings with a solid color (red) and set transparency to 60%
3) Take newer image and convert to a layer
4) Fill the markings with a solid color (green) and set transparency to 40%
5) Create solid underfill layer - black.
6) Optionally create a new layer, select by all-layer color black, and yellow-green, then expand the selection by 10 or more pixels and fill with new color (bright blue) to high-light even small differences.

Old material without match will be red; new material without match will be green, and matching material will be yellowish-green..

Unlike other comparison methods, the use of a bitmap editor allows non-significant changes to be recognized and cancelled out. It may be necessary to shift elements to get moved items to line up. It is suggested to move the older material so that comparison in the future will be based on the un-moved latest version.

If line weight (thickness, width) has changed, one can select and expand the selection for the thinner version to match the weight of the thicker version to cancel out spurious indication.

Refs:

Comparing Drawing PDFs for differences - PTC Community

Comparing Drawing PDFs for differences - PTC Community

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Re: Compare drawings in creo view - PTC Community

(my previous post) Comparing Drawing PDFs for differences - no maint - PTC Community

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[llie]

This is now possible with Creo View 4.1 and Windchill. We publish our drawings on check in as .plt's so we can use the Creo View compare functinality which automaticall lines up the two files and color codes the differences. We also need pdf's also of the final drawing when submitting the IR/CN.  

[dschenken]

Creo View cannot do this. It can only do a small sub-set; so can PDF compare in Adobe Acrobat.

By .plt, I assume you mean HPGL?

[llie]

Yes we publish HPGL's. If I save the PDF's to my hard drive from Windchill I am able to do a PDF compare in Creo View 4.1. I attached an image of the PDF compare.

[dschenken]

OK - now move that view to sheet 2, and make it a different scale.

Sure, the Creo View method can take beginner steps in comparisons, but it is weak in comparison with tools that are easy to use.

[llie]

Sorry I am not understanding. Creo View 4.1 drawing and PDF compare is super simple. Just open both files and select compare and it color codes only the differences. I moved the view to the second sheet with a custom scale like you asked. I also moved the other view out of the way and it pick up the changes. Sheet 1 only shows the model in red because the new version of the drawing doesn't have a model on the 1st sheet.

Everyone has their way of doing things. I was just responding to your post about comparing PDF's for differences. This is what we are implementing at our Company. We are already doing drawing compare out of Windchill with Creo View 3.0.

[dschenken]

It does not look like Creo View can adjust the location of the moved/resized view to de-emphasize those parts of the view that haven't changed. This is the typical problem with the old style of drawing comparison tools which the method I created can handle.

This is the disadvantage of super simple solutions - they only work on super simple problems.

When I have a drawing with dozens of sheets and a drafter has decided to move each of dozens of views a little bit because they think that's a help, or rearrange the dimensions, or rearrange the notes to move some of them to the next sheet or create another column, then I need a method to cancel the effects of those changes that do not affect the design information on the drawing, while being able to locate any changes that do.

Highlighting all the geometry just because an item moved a bit is not helpful. My method can also greatly emphasize something as small as changing a "." to a "," on a very large drawing so that the change can be seen at a glance.

[llie]

I am not able to rescale views, but I am able to align them view by view in Creo View 4.1. Once it is aligned, the color changes to black for the lines that are the same and then red/green only for the differences.

[dschenken]

So it doesn't end up with an independently verifiable result; just a manual one-shot? And can't be used to check multiple versions, just 2?

If that's the only tool available then you have to work with what you've got.