Computer Graphics with Photoshop - PS7 - converting background of an old map

Author

PS7 - converting background of an old map

AlanB

2007-02-09, 6:14 pm

I have scans of several old maps, approx. 150 yrs old, and I would
like to convert the backgrounds to white. Converting the image to
bitmap with a 50% threshold works with some maps, but not those with a
coloured background.

Can anyone suggest some simple techniques ?

A sample of one map is available at http://www.aqvh56.dsl.pipex.com/
originalmap.jpg

Thanks.

Bruce Uttley

2007-02-09, 6:14 pm

In article <1171056505.864844.229270@h3g2000cwc.googlegroups.com>,
AlanB <alan.simpson@merseymail.com> wrote:
>
>I have scans of several old maps, approx. 150 yrs old, and I would
>like to convert the backgrounds to white. Converting the image to
>bitmap with a 50% threshold works with some maps, but not those with a
>coloured background.
>
>Can anyone suggest some simple techniques ?
>
>A sample of one map is available at http://www.aqvh56.dsl.pipex.com/
>originalmap.jpg
>
>
>Thanks.

After first converting your originalmap.jpg to greyscale, your
technique of converting the image to bitmap with a 50% threshold
worked for me. I did darken the greyscale image a bit using
levels in between.

Am I missing something? What is not working with maps that have
a colored background?

granny

2007-02-09, 6:14 pm

> Can anyone suggest some simple techniques ?
>
> A sample of one map is available at http://www.aqvh56.dsl.pipex.com/
> originalmap.jpg

in PS7, I converted to Lab Color then used Levels with the black and
white point selectors (used black pointer on black and white pointer on
the gray background areas).. while still in Lab Color used unsharp mask
then converted back to RGB Color mode.. sample from your map here:
http://www.pixentral.com/show.php?p...1idSHBIr29AihV2

Also used Image/Adjustments/Replace Color (selecting the unwanted
colors) and adjusting the lightness and fuzziness to suit.. then using
unsharp in Lab Color

Both worked pretty well for me
--
"Granny"

ronviers@gmail.com

2007-02-09, 10:14 pm

On Feb 9, 4:47 pm, "granny" <DontSpa...@NoSpam.com> wrote:
>
>
> in PS7, I converted to Lab Color then used Levels with the black and
> white point selectors (used black pointer on black and white pointer on
> the gray background areas).. while still in Lab Color used unsharp mask
> then converted back to RGB Color mode.. sample from your map here:http://www.pixentral.com/show.php?p...1idSHBIr29AihV2
>
> Also used Image/Adjustments/Replace Color (selecting the unwanted
> colors) and adjusting the lightness and fuzziness to suit.. then using
> unsharp in Lab Color
>
> Both worked pretty well for me
> --
> "Granny"

Nice job. I still never think to get out of RGB.

Thanks for the tips,
Ron

AlanB

2007-02-10, 6:14 am

On 9 Feb, 22:03, b...@ist.uwaterloo.ca (Bruce Uttley) wrote:
> In article <1171056505.864844.229...@h3g2000cwc.googlegroups.com>,
>
> After first converting your originalmap.jpg to greyscale, your
> technique of converting the image to bitmap with a 50% threshold
> worked for me. I did darken the greyscale image a bit using
> levels in between.
>
> Am I missing something? What is not working with maps that have
> a colored background?

There is a noticable loss in quality using this method.

tacit

2007-02-10, 6:14 pm

In article <1171056505.864844.229270@h3g2000cwc.googlegroups.com>,
"AlanB" <alan.simpson@merseymail.com> wrote:

> I have scans of several old maps, approx. 150 yrs old, and I would
> like to convert the backgrounds to white. Converting the image to
> bitmap with a 50% threshold works with some maps, but not those with a
> coloured background.
>
> Can anyone suggest some simple techniques ?
>
> A sample of one map is available at http://www.aqvh56.dsl.pipex.com/
> originalmap.jpg

Convert t image to grayscale and use Image->Adjust->Levels.

--
Photography, kink, polyamory, shareware, and more: all at
http://www.xeromag.com/franklin.html

AlanB

2007-02-10, 6:14 pm

On 9 Feb, 22:47, "granny" <DontSpa...@NoSpam.com> wrote:
>
>
> in PS7, I converted to Lab Color then used Levels with the black and
> white point selectors (used black pointer on black and white pointer on
> the gray background areas).. while still in Lab Color used unsharp mask
> then converted back to RGB Color mode.. sample from your map here:http://www.pixentral.com/show.php?p...1idSHBIr29AihV2
>
> Also used Image/Adjustments/Replace Color (selecting the unwanted
> colors) and adjusting the lightness and fuzziness to suit.. then using
> unsharp in Lab Color
>
> Both worked pretty well for me
> --
> "Granny"

Thanks a lot.