June 1999
Intermediate to advanced
340 pages
10h 10m
English
Content preview from PNG: The Definitive GuideBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 4. Applications: Image Editors
To create a PNG image from scratch, one needs an image editor that understands PNGs. But there are many levels of understanding, and only a handful of editors exercise PNG's most interesting features. Here is a list of the support one would like to see in the ideal image editor:
- Basic image types: RGB, grayscale, and palette-based
- Images with fewer than 256 colors automatically saved as palette-based (or grayscale, if appropriate)
- Option to quantize and dither images with many colors down to 256 or fewer
- Simple transparency with any basic image type (i.e., single color marked as fully transparent)
- Full alpha transparency (also known as alpha channel or alpha mask)
- “Cheap” RGBA-palette transparency (i.e., where each palette entry has red, green, blue, and alpha components)
- Option to quantize and dither full RGBA images down to RGBA-palette images
- Option to enable interlacing
- Gamma correction, including calibration of display system
- Color correction: either chromaticity, sRGB, or full ICC profiles
- Ability to read, modify, and write 16-bit grayscale or 48-bit RGB images without conversion to lower bit depth
- Reasonable default compression settings: adaptive filtering turned on for all image types except palette-based; “medium” zlib compression level (say, between 3 and 7); unused palette entries omitted; if simple/cheap transparency, palette ordered so that opaque transparency entries can be omitted
- Options for both fast saves and best (slowest) ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.