PNGs

[Ryan Sims]

Hey Guys,
We all love looking at the 4K RED frame grab files that have been posted so far as TIFFs and DPXs.

But, 16bit PNGs may be a better option. Example: The Skytower DPX file posted is over 32MBs is size. A PNG (16bit color depth) of Skytower is less than 13MBs. That's nearly a 2/3 download time and hard drive space savings. The PNG is just as good, in fact, it is exactly the same.

Zlib is a lossless compression library, same idea as ZIP. PNG is always 100% lossless, "technically" and in every other way. It comes in 8 bit and 16 bit per channel flavors, and can include an alpha channel as well. Try it- take a 16-bit TIFF in Photoshop and save it to PNG, you will find the file is smaller, and yet if you open that PNG and subtract it from the original TIFF, you will find every pixel is zero. In other words they are bit-for-bit perfectly identical.

A PNG file is smaller than a zipped TIFF as well. A PNG of handtest is less than 30MBs. The zipped TIFF was almost 40MBs.

Just make sure you use the 16bit version of a PNG and not the 8bit flavor.

 

[MikeCurtis]

Is it as ubiquitously openable is the question for those who might want to drop it into something more than Photoshop?

Not a challenge, an honest question.

-mike

 

[jbeale]

Is it as ubiquitously openable is the question for those who might want to drop it into something more than Photoshop?

You mean to say there is anyone who doesn't have Photoshop? The PNG format has been around for 10 years- application support the first few years was slow in coming, but for the past several years, all the midrange photo and video software I have supports it, for some years now all browsers display it, heck even "Windows Picture and Fax Viewer" can display it. If you need, there is "ptot" (free) which converts PNG to TIFF. http://www.libpng.org/pub/png/apps/ptot.html

I haven't worked with the higher end grading software so I don't know how ubiquitous PNG support is there.

 

[Ryan Sims]

PNG - Portable Network Graphics

PNG - Portable Network Graphics

I think you will find PNGs much more supported than DPX and TIFF files.

Here's a few quotes from the PNG website http://www.libpng.org/pub/png/:

"Virtually all graphics-related applications these days are at least able to read or write basic PNG images"

"Browser support: very good to excellent
Web-browser support for PNG--or the incomplete implementation thereof--was, for more than a decade, a major thorn in the side of PNG developers and web designers who wanted to use PNG. While most browsers supported PNG images natively since the late 1990s--the "Big Two" (Netscape and Internet Explorer) having finally caught up in late 1997 (early 2000 for MSIE on the Macintosh)--the level of support was downright pathetic until 2001 or so and didn't achieve "ubiquitous goodness" until late 2006."

PNG's work super well for computer screen captures. A Bitmap screen capture will be over a 1MB. A PNG of the same screen might be 50KBs. A JPEG of a PC screen capture is very hard on the text. The PNG of text is perfect. I never use BMPs or JPEGs for PC screen captures.

PNG's don't help when trying to compress a JPEG photo. A PNG will be larger than a JPEG. But a JPEG is very destructive to an image. A PNG can be lossless(there are compression options) I was surprised that PNGs work so well on RED TIFF/DPX frame grabs. The low noise ratio in RED images is maybe why they are working so well.

Here's a sample screen capture PNG (it's only 85KBs):

 

[jbeale]

Just to clarify about "lossless"- the only loss I know with PNG is bit depth. The format supports 1,2,4,8, and 16 bits per channel, plus a 256-color LUT (like GIF). If you select a PNG flavor with fewer bits than your original, you are loosing colors just like you would converting a 24-bit image to GIF, for example. But there is no possibility in PNG for lossy compression, like the DCT+truncation process used in JPEG.

 

[Proteus]

Just to clarify about "lossless"- the only loss I know with PNG is bit depth. The format supports 1,2,4,8, and 16 bits per channel, plus a 256-color LUT (like GIF). If you select a PNG flavor with fewer bits than your original, you are loosing colors just like you would converting a 24-bit image to GIF, for example. But there is no possibility in PNG for lossy compression, like the DCT+truncation process used in JPEG.

If you don't want compression artifacts in your image, its the preferred wide-supported image type with a very efficient lossless compression.

JPG can produce smaller files, but with artifacts. JPEG2000 is about 2 times more efficient than JPG (in my testing, half the size or double the quality) -if the viewer has the appropriate plugin in his application. It's also capable for lossless compression but PNG's lossless efficiency is higher.

 

[conrad gaunt]

Just to clarify about "lossless"- the only loss I know with PNG is bit depth. The format supports 1,2,4,8, and 16 bits per channel, plus a 256-color LUT (like GIF). If you select a PNG flavor with fewer bits than your original, you are loosing colors just like you would converting a 24-bit image to GIF, for example. But there is no possibility in PNG for lossy compression, like the DCT+truncation process used in JPEG.

PNG does compress in a very different way (Runlength encoding) but I believe it is capable of higher/lossy compression too, isn`t it?

EDIT, It looks like you`re right, the word lossy cannot be found on the PNG site at all. I`m surprised.

 

[Thomas Mathai]

DPX and TIFFs are standards for post work. I haven't seen PNG except for Flash animation.

 

[goal]

PNG looks great indeed. We especially like it when we make composites of layers on a canvas that are far greater then the actual screen so you can pan over them or make extreme zooms. PNG keeps the system running more happily then when we use TIFF for that.

 

[Ryan Sims]

Post work

Post work

DPX and TIFFs are standards for post work. I haven't seen PNG except for Flash animation.

Thomas, you are 100% correct. PNGs are too slow for post work. The PNG has to be read and DECODED. TIFF's and DPX just have to be read off a hard drive. If you have a fiber SAN connected to the workstation, no real need to use PNGs then.

PNGs are great for sharing files across the Internet (which is what they were designed to do) where bandwidth and storage size are premiums.

 

[jbeale]

PNGs are great for sharing files across the Internet (which is what they were designed to do) where bandwidth and storage size are premiums.

I think that's where this thread started out: What is the best format to share your latest Red frame grab (with all the original dynamic range) with the audience here on reduser. PNG seems best for that to me.

PNG is also useful if you need to archive the maximum # of processed frames on a given storage media (DVD-R etc) while still maintaining full original quality. Of course if it's straight from a .r3d file, then just that portion of the actual .r3d file would be even better, as far as size goes. Bringing up the question: can you segment a .r3d movie file into separate single frames and store those as separate files on the disk? I assume so, given Redcode apparently doesn't do inter-frame compression.

 

[Ryan Sims]

.r3d files

.r3d files

Yes, the sooner we can post and share .r3d files, the better. We just all need access to REDcine or alert before that can happen. When .r3d files are the standard, forget TIFFs, DPXs and PNGs. We'll most likely then just share JPEGs for the CC looks we created from the .r3d raw files.

 

[PatrickFaith]

Resurrecting an old thread ... but this is the closest one I could find were someone was playing with png. I have been doing speed tests for vfx intermediate work ... and am often finding my best times are r3d -> png then back from png to composite with r3d. I am doing separate passes for shadows and z-depth, so don't really need those options from openexr. Also when I need to code some vfx i'm finding more interfaces for png. The png sizes at 4k are often 3x smaller then openexr and 5x smaller then dpx, so this saves me a lot of speed on reads, and reduces my disk requirements. Since png is not lossy, seems like it works way better then jpeg2000 (which is sometimes hard to find the plugin for), and png is only about 2x bigger then jpeg2000. PNG also has alpha channels, which i use a ton. For "indie" vfx, does it make sense to use png ?