Posts Tagged ‘TIFF’

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

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Briefly About TIFF

Hi folks,

Let’s resume the short descriptions on most popular raster image file formats and today take a short overview of the “senior” TIFF bitmap format, which will soon be 30 years old, quite an admirable age when it comes to computing.

TIFF (“Tagged Information File Format”, file extensions .tif or .tiff) format was officially released back in 1986 by Aldus Corporation (now Adobe) with the intention of providing a standardized format for files resulted from scanning process, as at that time the many existing proprietary formats were creating serious compatibility issues.

Aldus did a great job as TIFF quickly became widely adopted, being a platform-independent and very flexible format.
In fact it is so flexible that its most recent specifications are dated 21 years ago (in 1992) as a result of the fact that no important improvements were requested by users.
Such flexibility (which actually also translates into complexity) makes us tell you but few words about TIFF, to draw a quick portrait sketch by using just few lines.

To put it in a nutshell, TIFF allows to store single/multiple pages at any required quality and to add any imaginable tags from the most basic to private ones. It supports all kinds of color encoding (ranging from B/W, through greyscale and up to color schemes) and many compression algorithms, such as LZW we’ve told you about not so long ago, CCITT or JPEG-based.
By offering such a luxuriant palette of options, TIFF is the best container to store highly detailed image information and it keeps on being the number one option for digital image preservation.
So no wonder why TIFF format is chosen whenever serious storage is required, albeit scaning important documents, desktop publishing or even storing master-versions of photos.
Of course this clean and open format has its drawbacks too, the biggest one being about size.
But keeping in mind the various lossy and losless compression options TIFF has to offer as well as the fact that digital storage space is already cheap and gets cheaper and cheaper every day, the size aspect is not a really bothering one at least not for professionals.
And its 4 GB maximum size limitation didn’t prove to be a main reason of frustration among users (but should it become one, it can be enhanced by Adobe, which currently holds all rights on TIFF specifications).

All in all, TIFF is not the format one would prefer for sharing images over the web, but its baseline specifications along with the wide range of subformats which extends up to exotic boundaries such as the GeoTIFF developed by NASA makes it perfect to store master copies for long-lasting purposes.
But being highly successfull, TIFF is also highly convertible so anyone can create more web-suited versions of his treasured images, by converting to formats such as PNG or JPEG.

Needless to say we support TIFF format and conversions in all our products, offering complex handling options for developers that use our GdPicture.NET SDK within their projects, as well as offering total simplicity for our general public users of PaperScan to annotate or convert TIFFs to or from other 90 file formats including PDF.

Next week we are going to tell you some practical basics on PNG.

See you then!

Bogdan

Big Browser on July 26

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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

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Casual Friday on April 19

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