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Thread: Raster design bitonal image for contour follower

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    Default Raster design bitonal image for contour follower

    I'm trying to convert raster to vector from a scanned pdf file. Have converted the pdf to a bitonal (black & white) tiff image using Adobe Acrobat and IrfanView. The tiff image inserts into Map3D 2011 without a problem, but when I try to run the Raster Design contour follower, CAD says "no bitonal image recognized". My image is 300 dpi (within the 200-400 recommended) and is definitely B&W, not grayscale.

    Then if I use the AutoCAD tools to convert the image to bitonal, CAD changes the background to BLACK and the contours to WHITE. Then the contour follower will not work. Sometimes it starts, takes forever, and makes a few strange lines that don't track with the contours at all.
    The tutorial for contour follower works perfectly on my PC. But it isn't working with my tiff. Any suggestions would be appreciated.

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    Administrator Ed Jobe's Avatar
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    Default Re: Raster design bitonal image for contour follower

    The colors might appear "black and white" but not be bitonal. "Bitonal" means a color bit depth of 2. Your image could have a bit depth of 8, 16, 32 or more colors, but be using only 2 of them. Check the images properties and make sure the bit depth (no of possible colors) is 2.
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    Geospatial Moderator Jmurphy's Avatar
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    Default Re: Raster design bitonal image for contour follower

    You can use the Invert command under the image cleanup tools to change the contours back to black in color. Also look at the options for the contour follower tools. The Vtools Follower tab on the RD options, you tolerance may need to change.

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    Default Re: Raster design bitonal image for contour follower

    Hey folks, the AutoDesk support team helped me with my problem. Seems the bitonal image was reversed. But the size changed from 49 mb to about 760 kb, so perhaps something else was going on also. Here's the answer from AutoDesk:

    *****
    I tried inserting the TIFF image with IINSERT, but it looks almost all white. If I zoom in a bit, I can start to see the lines, but not when zoomed to extents. I took the TIFF file into Photoshop and inverted the colors. Now, when I IINSERT it into AutoCAD, it looks correct, even when zoomed to extents. If my AutoCAD background is black, then the contour lines are white, and if my background is white, then the lines are black. Either way, the contour follower should be a lot easier to use with this image file now that its colors have been "flipped".
    *******
    and in a second e-mail:
    *********
    I'm very glad to hear that the inverted image worked. All I did was open the TDS4501463.tiff in Photoshop, and then I clicked Image > Adjustments > Invert (CTRL+I does the same thing). We have the CS4 version of Photoshop, but I don't think that particular command varies greatly from version to version.

    Best regards,

    Zac Travis
    Autodesk Support Team

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    Default Re: Raster design bitonal image for contour follower

    Quote Originally Posted by swyman View Post

    Then if I use the AutoCAD tools to convert the image to bitonal, CAD changes the background to BLACK and the contours to WHITE.
    Try setting your CAD background to WHITE for now, does the background in the image stay black?

    Presuming it does, then try setting transparency on for the image you've attached, and assigning a color to the image - say color 219. That _should give you a white background, with dark graphics.

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