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I am 1 week new to Inkscape, so forgive my ignorance here. I am working with a Glowforge to engrave vintage photos like this:

https://fineartamerica.com/featured/vintage-blueprints-1-andrew-fare.html?product=art-print

I basically need this as black and white, not black and yellow. When I try to remove background, I can get rid of the yellow, but shaded grays remain that is picked up by the engraver.

How do I pull out just the ink (black) portion of these kind of pictures?

  • Thank you for the guidance! I will get to Gimpin'! – justinb Feb 17 at 14:21
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You can't do it in Inkscape. Inkscape is a vector image editor, it can't edit raster images.

Use GIMP instead. It's free and Open Source like Inkscape.

Open the image, then do Colors > Components > Mono Mixer, and use the settings shown below

enter image description here

You could then do Colours > Levels to try to get rid of the smudgy grey bits left over. Move the tiny triangular sliders under the Input Levels as shown below.

enter image description here

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The level of detail of the referenced image is high, yet the image online is heavily dithered/pixelated to the point that it is unsuited for laser engraving, other than as a bitmap engrave.

Vector images provide for great detail in the engraving process, but the blueprint cannot be well converted to a vector format.

As a bitmap engrave, if your software supports it, you will have gradient burning and it will include the shading.

It's impractical to consider manually tracing such a detailed drawing, but it appears to be your only option from the online image.

You could, as the most viable path, purchase the largest size of the product, then scan/photograph it, to provide a better level of detail for conversion to vector.

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  • Thank you for the education! – justinb Feb 17 at 15:05
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I guess it's useless to try to trace images this complex (=full of noise) to vectors. At least you should have much more resolution than your linked axample has and you should reduce the amount of the crap radically, Finally: Your engraving system seems to be designed for bitmap images.

Cleaning the bitmap image can be started by making a BW mix where the yellowish texture gets whitened. Photoshop's Image > Adjust > Black and White is for the job. Vector drawing programs have less possibilities for bitmap image fixing.

enter image description here

Several other programs with hue selective adjustments exist. Buy and install nothing by trying web service Photopea. It replicates a good slice of Photoshop's basic functionality.

Curves tool can be used to deepen the blacks and lighten the greys. If your engraving system understands and renders greyshades, this step very likely makes the result worse if you kill too much greys.

enter image description here

At least now the need of high resolution image is obvious.

The random dots and possible missing black pieces must be fixed manually by inserting black and white. Automatic denoise filterings very likely remove also some wanted details.

Multilayer editing program is a delight because nothing is destructive. Even the adjustments can be adjustment layers in Photoshop, tweaking both of them for the best combined effect is possible there. With layer masks you can apply different adjustments to different areas.

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  • Thank you for the insight! – justinb Feb 17 at 14:22
  • You are right that higher resolution is needed, but sometimes it helps to separate the details if you scale up the image at least 400% before editing. See here. – Wolff Feb 17 at 16:49

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