Color zooming or halftoning

Question

Mesho 2023-10-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2037101-color-zooming-or-halftoning

评论： Mesho 2023-10-26

采纳的回答： Walter Roberson

Dear all,

I have this image from wikipedia that explains halftoning.

https://en.wikipedia.org/wiki/Halftone#/media/File:Halftoningcolor.svg

I want to experiment the same thing with matlab for other color combinations. So what will be the output color I will see from a far distance when combining different dots with different size and rotations?

Any suggestion will be appreciated.

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Answer 1

Walter Roberson 2023-10-24

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https://ww2.mathworks.cn/matlabcentral/answers/2037101-color-zooming-or-halftoning#answer_1339781

Decided on a per-layer transparency, something like

transparency = 0.8;

Create each halftone in an array.

image() the lowest layer (the one to go underneath)

hold on

now loop over the other layers:

alphadata = transparency .* double(thislayer ~= 0);

image(thislayer, 'AlphaData', alphadata);

At the end of the loop, turn hold off

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Walter Roberson 2023-10-25

The potential problem with zooming it out is that you are then subject to whatever graphics smoothing that MATLAB chooses to do. You can turn off the explicit smoothing, https://www.mathworks.com/help/matlab/creating_plots/using-graphics-smoothing.html but at some point it is going to have to interpolate data from pixels to fit into the physical screen.

You might well need 200 or more dots per inch https://www.atlasscreensupply.com/blog/choosing-the-right-mesh-and-halftone-dot.htm for your halftone. Ah, more values at https://en.wikipedia.org/wiki/Halftone#Resolution_of_halftone_screens -- you will probably need more than 300 dots per inch.

Typical desktop screen resolution does not get that fine. My relative high resolution iMac, 5120 x 2880, is about 218 dots per inch.

Some laptops do get up to those resolutions -- and some smartphones do get up there. For example the recent iPhones have had resolution of roughly 460 dots per inch... on a screen that is about 6.5 inches diagonal.

If the number of pixels in your halftone images exceeds the physical limits of the display you are using, then some layer is going to have to reduce information down. So to avoid that, do not bother with an image that is more than roughly 1000 x 1200 /

Mesho 2023-10-26