Routes

Pictures: gif or jpg?

I decided to write this page to explain some things that often may create confusion and make a page slower or of lower quality.
Some faults about pictures format can very often be found also on sites that should be very professional (Flying companies, tourism organizations, etc.
Tiger, my cat, will help me to explain.

Here below you see a photo of Tiger and some Vagabondo's icons registered in different formats and flanked by the dimension of the file that comes out from them ...

	Tiger	Icons
JPG	9.6 Kb	7.9 Kb
GIF 256 c.	32.0 Kb	2.4 Kb
GIF 16 c.	12.1 Kb	1.5 Kb

• Tiger
  Tiger in JPG format takes 9.6 Kb and you can see him pretty well, when we bring it in GIF with 256 colours quality remins quite good (though it loses something: from 16 millions to 256 colours), but the file becomes more than three times heavier, going as far as 32.1 Kb.
  In GIF with 16 colours the weight of the pictures lowers to 12.1 Kb, but, poor Tiger, he is pretty ugly by now!
  
  
• Icons
  In JPG format icons take 7.9 Kb and are really loathsome, whilst, in GIF with 256 colori are much nicer and only take 2.4 Kb, three times less!
  With 16 colours, to end with, the quality remains the same, but the pictures takes as little as 1.5 Kb!

Final considerations

The GIF is a format tending to diminish the number of colours: so we will employ it for all the pictures that don't have many colours neither nuances: maps, buttons, notices, logos and icons. Some programs, for instance Photoshop, consent to specify the number of colours to which the pictures must be brought.

As for JPG, on the contrary, it compresses the images as it is, losing some data but mantaining all the colours, so we'll employ it for photos and pictures. A good compromise, in my opinion, between quality and dimension of the images for Internet, is compression to 40%.

BMP, to finish with, is absolutely not suitable for Internet, because of files dimension and should never be employed on line (Tiger would take 150 Kb!); it will be employed only on one's own computer to to preserve a copy of the image that has then been compressed in JPG (so loosing part of the data)to be put online.

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