Posts Tagged ‘GIF’

Which bitmap format to choose

Hi folks,

Following the short suite of articles that briefly described the most popular raster graphics file formats, today we will try to make a synthesis and see which format would be a best choice for which purpose.

Image capturing
When capturing images, either by scanning a document or taking a photo, the best idea would probably be to get the highest quality possible and keep the full amount of details.
The initial capture file is a “master” file so, unless you can repeat the same capture process anytime or don’t care about long term preservation, you can store it somewhere safe and convert it to other formats for current manipulation.
And if you think that such practice is for professionals only, you’d better think again.
IT evolves at highest speed: image acquiring quality is increasing, bandwidths are getting larger and cheaper, storage spaces too and image quality standards are adapting accordingly so what was considered a professional level of quality few years ago, today is widely common.
So you shouldn’t be afraid to use TIFF format as best choice for richest captures.
But there’s always PNG at disposal too of course.

Image handling
Chosing a format for image handling depends mainly on the kind of image involved but also on its manipulation purpose.
For example, JPEG is notoriously the best choice for photos offering an optimum quality vs. size ratio, we’ve explained you previously how this was achieved.
JPEG can be used especially for smooth-toned images but due to its small sizes, even if quality-lossy, it can be used for any kind of images including documents.
Actually, when it comes to documents to be shared at real minimal size with least acceptable quality, there is JBIG2.
Making a visual comparison between a JPEG and a JBIG2 format version of a same document might seem to turn JPEG into a winner.
But for large amounts of documents or for transfering documents through busy networks, JBIG2 is a life-saviour.
In case the quality of the document is really important, PNG should do the trick.
For web graphics, GIF and PNG are largely prefered.
They both are palette-based and the file-sizes depend on bit depth and on the number of colors of the palette, one basic difference being that GIF allows animations while PNG supports gradual transparency.
So they both are well-suited for webdesign items like logos, buttons, banners and so forth, the choice depending on graphic artist’s intentions.
For short animations (today used mostly for tutorial/explanatory purposes) GIF is the only choice, similar to how PNG is the only choice for graphics where variable transparency is required.
As you’ve probably noticed, we’ve mentioned PNG several times above as it can be used for full-colour images with lossless compression, continuous-tone full-colour images at the highest quality (not highest compression), B/W and greyscale images, for desktop and web purposes, thus making PNG a reliable and versatile quick choice solution when there is no real pressure for a certain requirement.

Image printing
Normal printers are designed to work fairly well with all kind of image file formats.
But if printing quality is a serious requirement (talking about desktop printing quality level, not highly professional level) then the “give me most possible data from uncompressed source and I’ll give you best possible result” principle applies.
In other words: use TIFF.
Which is yet another reason for you to consider the initial recommendation above of keeping “master” files.

Well, the circle being closed now, let’s just add that we’ve tried to keep everything as basic as possible.
There are many aspects and details we’ve intentionally skipped because the scope of our blog articles is simplicity.
But if complexity is what you need, please feel free to use GdPicture.NET SDK to build applications controling every possible detail of images in more than 90 supported file formats.
And if you’re not into software development, have no worries: we’ve already built such application for you.
It is called PaperScan and it can be downloaded from here.

See you next week, folks!

Bogdan

Big Browser on August 23

Some iRumours Read article Average Income per Programming Language Read article The Story of the PING Program Read article Meet the NASA scientist devising a starship warp drive Read article Google can't have dotless domains, rules ICANN regulator Read article

Briefly about GIF

Hi folks,

Today we will try to give you a quick overview on the GIF file format.

GIF format was introduced by CompuServe in 1987 and soon became widely adopted because it supported colours (unlike its CompuServe predecessor, RLE) and it was small-sized (thanks to the LZW lossless compression algorithm, we’ve told you a story about that in a previous article), allowing reasonably fast file transfers even for the slow, dial-up modems era.
CompuServe was a company way ahead of its time.
It was founded in Columbus, Ohio, in 1969 (the “prehistory” of the internet) by an insurance company (“Golden United Life Insurance”), initially to provide computing power for in-house optimization of the data-management needs of the mother company but shortly CompuServe became a serious business on its own, some naming it “the Google of the 70’s and 80’s”.
First they rented computing power time to other companies (when computers were idle), then a long series of pioneering achievements followed, here is an incomplete enumeration: one of the first companies to offer online services, world’s first online service offering internet connectivity, issued and hosted thousands of moderated forums, created a file transfer protocol, developed its own (proprietary) email services, hosted the first WYSIWYG email and forum posts content, pioneered the online shopping, created customized portals, pioneered online financial services, created an online chat system, introduced online games and published the first online newspaper and the first online comics.
And invented GIF, of course.

GIF (“Graphics Interchange Format”) is a bitmap graphics file format, its first version being referred to as GIF 87a, to indicate the year of release, 1987.
Two years and many enhancements later, GIF 89a version was introduced and it accounts for the vast majority of GIFs currently existing on the internet.
It provides image designers with 256 colors, allows multiple images storage for animation purposes (not in the sense of multipage, as in TIFF), provides controls for animation (animation speed and single/infinite loop option), allows on-or-off transparency (no intermediary gradients of transparency, as in PNG), provides lossless compression and introduced interlacing as an option.

Interlacing, when it concerns image files, means the image is gradually rendered by a browser but rendering starts immediately after download starts so, at first, the image looks unclear, like being out of focus, then, as its download continues, it becomes sharper and sharper, finally showing in full quality when image download is complete.
Previously described Progressive JPEG and the soon to be described PNG formats provide optional interlacing feature, too, but while in GIF and Progressive JPEG case interlacing changes the rendering order of the horizontal lines, the PNG format allows changing the order both horizontally and vertically.

As for compression, GIF uses the LZW lossless compression algoritm eversince it was created.
LZW was a perfect fit for its 8-bits-per-pixel color encoding (ie, maximum 256 colors displayed at one time in a frame) as well as for the animation feature, because GIF animation works by successively displaying bitmap images slightly different from one another (frames), their most part remaining unchanged so, being repetitive, most data are subject to very efficient compression by LZW.
GIF format isn’t commonly used for photos because compressing only 256 colors, even in a lossless manner, provides much poorer results than lossy compressing some 16 millions colors, like JPEG does.

Although the LZW algorithm was/is a major contributor to GIF’s popularity and widespread, it also gave it almost 10 years of torment (since about 1994 until about 2004) caused by the Unisys patent protection controversy.
But nowadays GIF format enjoys times of peace and recognition which will probably continue to last as long as people will keep their apetite for logos, icons, animated emoticons, low-res short clips, educational animated clips and so forth.
In 2012, this venerable format received public tribute from the Oxford Dictionaries USA subsidiary of Oxford University Press, the word “GIF” being granted the “Word of the Year” title, both as a noun and as a verb.
So now the question is: to GIF or not to GIF ?

We will try to answer this shakespearian question in a future article about which bitmap format fits best for which purpose, as PaperScan supports them all.

See you next week!

Bogdan

Big Browser on May 31

Apple 1 from 1976 signed by Wozniak sells for $650,000 Read article Game of Thrones Pirates Break BitTorrent Swarm Record Read article Google’s new “Moto X” superphone will spy on you 24/7, and you’ll like it Read article The Rise of the Mobile-Only User Read article Wary of Bitcoin? A guide to some other cryptocurrencies Read article

LZW and 3 graphics file formats

Hi folks,

This week we are going to tell you a short story about LZW compression and how it influenced 3 widespread graphics file formats: TIFF, GIF and PNG.

The story begins in 1977 and 1978 when israeli computer scientists Abraham Lempel and Jacob Ziv published descriptions of lossless data compression algorithms named LZ-77 and LZ-78, respectively.
Terry Welch, an MIT trained computer scientist, further developed the LZ algorithms and, in 1984, he published the Lempel-Ziv-Welch (LZW) algorithm.

LZW compression became the first widely used universal data compression method on computers.
Being so influential, the “LZ-” based various algorithms became, of course, subject to patent protection in many countries.
For LZW, two patents were issued in the USA (but in other countries as well), the one filed by Welch himself being assigned to Sperry Corporation (Welch’s employer) in 1983.
Sperry Corporation became Unisys in 1986.

So.
Just to have a glimpse on the algorithm, consider this string: “The cat chases the mouse in the room”
The word “the” occurs 3 times.
Replace it by “!” and the string becomes: “! cat chases ! mouse in ! room”.
Add this association (“the” to “!”) to an index and you’ve reduced the length of the string from 36 to 30 characters.
Of course, things are way more complicated than this but the main idea is that the algorithm works very well when there are many repetitive data.
And image files usually contain lots of repetitive data.

In 1986, Aldus Corporation released the first official TIFF specification and in 1988 revision 5.0 was released, which included the ability to use LZW compression.
In 1987, CompuServe created the GIF file format, the GIF specification requiring the use of the LZW algorithm to compress the data stored in each GIF file.

The holder of Welch’s LZW patent, Unisys (which maintains a portfolio of about 1500 patents), was motivated to monetize this patent as much as possible and it had to be fast, too, as the patent availability was 20 years.
Overall, the total number of licensees was about 100, among which Adobe was licensed in 1990 for the use of LZW patent for PostScript and Aldus was licensed in 1991 for the use of the Unisys LZW patent in TIFF.
Licensed LZW in TIFF generated a wave of discontent so Aldus quickly introduced JPEG compression in TIFF (as of revision 6.0 in June 1992) but it had serious design errors and limitations, making things even worse (this was later corrected and replaced with a totally new TIFF/JPEG specification).

But it was not before 1993 that Unisys finally became aware that the GIF file format, very popular already, was using their patent-protected LZW algorithm.
And CompuServe had no clue they were infringing on LZW patent.
In 1994 Unisys and CompuServe came to an understanding which, for various reasons, generated a huge protest reaction, the matter being reported by many newspapers including the Time Magazine.
Many upset developers and users removed their GIF files or converted them to JPEG (yes, JPEG again, it’s royalty-free!).
But JPEG uses lossy compression, so one of the protesting groups, formed by leaders of the online graphics community, began working on a lossless and patent-free version of GIF.
Their efforts produced the PNG specification.

As an epilogue, by 2004 all Welch (ie, Unisys) LZW patents expired in all countries where they were issued (IBM patent on LZW expired by 2006).
TIFF specifications are now controled by Adobe and LZW can be freely used with it.
Adobe uses for PDF a LZ-77 based compression algorithm named “DEFLATE”.
GIF format is still popular.
PNG became one of the most important graphics file formats in the world.

In the upcoming articles we will provide some explanations on bitmaps as well as some short overviews on the most common bitmap file formats, including TIFF, GIF and PNG.

Bye for now!

Bogdan

Big Browser on April 19

Netflix says it’s dumping Microsoft Silverlight and embracing HTML5, someday Read article Hijacking airplanes with an Android phone Read article A non-mathematical explanation of one way functions Read article Silicon Valley Goes Hollywood: Top Coders Can Now Get Agents Read article Plan your digital afterlife with Google's Inactive Account Manager Read article

Casual Friday on April 19

A duck family crosses the street