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On 27.11.2023 1:57, Kenneth wrote:
> "David Kraics" <bar### [at] aol com> 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
defects.
As a result, POVRay will have much less reasons to "think" about this
image and "do" something about it.
Ilyich
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