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PNG Transparency

Screenshots from Oregano2 for RISC OS

These are half-scale JPEG screenshots of the pngs-img.html, png-rgba32.html, and png-MagnoliaAlpha.html pages. They were taken by E.Mark Jolliffe using Oregano version 2.0 or 2.1 under RISC OS.

Click on the half-scale JPEG images to see the full-scale, 24-bit PNG versions (461338, 1099495 and 597666 bytes, respectively):

[pngs-img.html half-scale screenshot (75k)]
[png-rgba32.html half-scale screenshot (70k)]

[png-MagnoliaAlpha.html half-scale screenshot (40k)]

Oregano's rendering of alpha transparency appears to be excellent on both plain and textured backgrounds. The only obvious bug is the lack of gamma correction on the two lefthand (palette-based) toucans. All three single-toucan images were created on a NeXT system (with a native "gamma" value of 1.0--PCs are typically 2.2), resulting in very dark images if the viewing application fails to do gamma correction.

Other than the palette glitch, Oregano does gamma correction consistently for all image types and HTML and CSS colors, as this shot of Glenn Randers-Pehrson's gamma-test page shows. Its linked PNG image is 74814 bytes:

[gamma_test cropped screenshot (27k)]

Here are some related PNG pages at this site:

[primary site hosted by SourceForge] Last modified 14 March 2009.

Copyright © 2005-2009 Greg Roelofs.