signal processing - Reducing moire when downsampling halftone comic images -

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how can reduce moire effects when downsampling halftone comic book images during live zoom on iphone or ipad?

i writing comic book viewer. nice provide higher resolution images , allow user zoom in while reading comic book. however, client averse moire effects , not allow feature if there noticeable moire artifacts while zooming, of course there are.

modifying images less susceptible moire work if modifications not perceptible. blur prohibited, removes beloved halftone dots.

the images black , white halftone , line art. originals 600 dpi ship application half @ best, 2500 pixels or less tall.

so options? if write custom downsampling algorithm fast enough real time on these devices? there other tricks can do? work avoid size ratios have visual moire effects?

as zoom in out, there peaks moire effects worst. there way calculate points , zoom nearby scale not bad?

any suggestions welcome. have little experience image , signal processing, enjoying opportunity learn. know nothing of wavelets , acutance , other jargon, please verbose.

edit:

for @ least punting on dynamic zoom. support zooming in full magnification not arbitrary scaling. hope revisit in future.

difficult problem, in general, interesting in particular. doubt there good-simple solution - perhaps if assume ideal halftoning (monochrome images halftoning dots placed in perfect grid), hardly work scanned image.

if interested in math and/or want bibliography research, this thesis might useful (i haven't read it)

also can search descreening algorithms, plugins, etc, ideas.


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