topic Re: removing regions on bitonal vs color images in AutoCAD Raster Design Forum

removing regions on bitonal vs color images

sfore — Thu, 04 Apr 2019 14:04:11 GMT

I have 2 images of the same as-built electrical site drawing. I'm trying to use Raster Tools to remove regions and draw in asbuilt information. The first is a tiff converted from a pdf.. The second is a scan from the pdf print.

The first has a white background and quality is nice showing existing features in gray and proposed features in black. The second image does not have a white background and does not show any gray scale. It does not because I purposely scanned it in as a High Quality black and white tiff so the image would be bitonal.

When I remove regions via raster on the first image, it leaves a black "hole" on the plot preview. I've tried playing around with transparency etc... with no success.

I am able to remove regions on the second image just fine but the overall quality of that image is poor.

Is there a way I can use the first image and remove regions without seeing black holes? See pics.

Re: removing regions on bitonal vs color images

Ed__Jobe — Thu, 04 Apr 2019 14:09:19 GMT

I've seen that problem before, but I don't remember how I fixed it. Can you post the image so that I can test it?

Re: removing regions on bitonal vs color images

sfore — Thu, 04 Apr 2019 14:59:20 GMT

Here ya go. Image is attached.

I may have figured something out. See below pic. I gripped image and turned Background transparency to yes, then clicked transparency color and selected a part of the white image. Then used rater tools and removed a region on the image and printed. It came out fine. The only thing that is different this way, is the gray's aren't as gray as original printed gray's. I'm ok with that, but if you know a better way, please advise. Thanks

Re: removing regions on bitonal vs color images

Ed__Jobe — Thu, 04 Apr 2019 20:54:40 GMT

What you did is one way that I was going to suggest. The other way is to convert it to bitonal. This is what I prefer because that's what the file really started out as. You can't just do it in one step though without loosing data. What I did first is to use IDEPTH to convert it to grayscale. This limits the number of colors to 256. Then I ran the Palette Manager (IPAL). I used the Combine option to reduce the number down to 0,0,0 and 255,255,255. I selected the first four top rows and then combined, selecting color 1. Then I selected the bottom 3 rows and combined them to color 255. Next I used the IDEPTH command again, choosing bitonal. Save the file.

Examine the detail to make sure nothing was lost. You may need to play around with the palette manager to change which colors get combined.

Re: removing regions on bitonal vs color images

sfore — Thu, 04 Apr 2019 21:50:13 GMT

I tried it but was unsuccessful. I'll keep experimenting. Thanks for the information.