POV-Ray : Newsgroups : povray.general : Image_map question : Re: Image_map question Server Time
22 May 2024 00:31:24 EDT (-0400)
  Re: Image_map question  
From: Ilya Razmanov
Date: 27 Nov 2023 00:16:25
Message: <65642629$1@news.povray.org>
On 27.11.2023 1:57, Kenneth wrote:
> "David Kraics" <bar### [at] aolcom> wrote:
>> The original jpeg is a blueprint with firm solid black lines. The image is
>> greatly faded. Am I missing a function or someting?
> I have no idea why some of the blueprint lines would turn to grayscale rather
> than pure black.
> But try this trick:

Unfortunately, we don't know where the jpeg comes from. However, even 
with JPEGs (which are not intended for line drawing) there may be much 
easier solution:

1) Download and install GIMP. Following steps are given assuming you did 
it and started GIMP.
2) Scale image up, much larger than necessary. Apparently fix the 
proportions, so you don't need to interpolate image with POVRay.
3) Use Colors\Levels to make background white, lines black, and shift 
greys toward these ends so the lines look better.
4) Use Filters\Generic\Erode (that's how "Minimum" is called in GIMP) to 
make lines thiker.
5) Use "Levels" again to you taste.
6) Use Colors\Threshold to turn image into black and white (not 
greyscale or RGB, like JPEGS)
7) Save oversized B/W image as PNG to avoid further introducing JPEG 

As a result, POVRay will have much less reasons to "think" about this 
image and "do" something about it.


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