The Mystery of Mac OS' Mangled Image Interpolation Implementation

-=- Here in Userlandia, I'm talking rainbows, I'm talking pixels. -=-

What is a bug? A miserable little pile of code... or something more? Today we look at a curious quirk in how Mac OS displays images in PDFs. The case: an ordinary strip of colored squares has transformed into a smooth rainbow gradient. Can you channel your inner detective and solve the mystery?

Blog Post: https://www.userlandia.com/home/2021/11/the-mystery-of-mac-os-mangled-image-interpolation-implementation

Published November 16, 2021

-=- Chapters -=-

00:00:00 - Intro 00:00:42 - When There's Something Strange... 00:03:42 - Layers of Quartz 00:09:43 - Resolving Power 00:14:06 - Objection! 00:17:37 - Interpolation Interpretation 00:23:53 - The Fix Is In 00:26:35 - The Final Cut 00:29:02 - Outtro

-=- Links -=-

• Color Scale Smoothing - Ars Technica Openforum - https://arstechnica.com/civis/viewtopic.php?f=19&t=1477509
• generic-mapping-tools - http://generic-mapping-tools.org
• Quartz - https://arstechnica.com/gadgets/2000/01/macos-x-gui/
• Display PostScript - http://www.nextcomputers.org/NeXTfiles/Docs/NeXTStep/3.3/nd/Concepts/Pre3.0_Concepts/04_Drawing.htmld/index.html
• CoreGraphics - https://developer.apple.com/documentation/coregraphics
• Image Resolution and DPI - https://guides.lib.umich.edu/c.php?g=282942&p=1888163
• Matrix Transformations - https://personal.math.ubc.ca/~cass/graphics/text/old.pdf/last/ch4.pdf
• PostScript Level 3 Reference Guide - https://www.adobe.com/content/dam/acom/en/devnet/actionscript/articles/PLRM.pdf
• PDF Reference Guide v1.4 - https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/pdf_reference_archives/PDFReference.pdf
• psscale - GMT - https://docs.generic-mapping-tools.org/latest/psscale.html?highlight=psscale
• Ace Attorney - https://en.wikipedia.org/wiki/Ace_Attorney

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Theme Song by Space Vixen: https://spacevixenmusic.bandcamp.com Follow them on Twitter @SpaceVixenMusic: https://twitter.com/spacevixenmusic

Music Credits:

Artist: Ron Gelinas Track Title: Gaining Momentum https://youtu.be/RTRl0mD9Y8g

Ace Attorney — Pressing Pursuit — Cornered - https://www.youtube.com/watch?v=UxnvGDK0WGM

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Dream Cruiser by Anders Enger Jensen - https://www.youtube.com/watch?v=FalGOzjuG64

Retro Runner by Anders Enger Jensen - https://www.youtube.com/watch?v=1l7fOHedd2I