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Author Topic: What's The Difference Between a JPEG and a BMP ?  (Read 7435 times)

Offline neilep

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What's The Difference Between a JPEG and a BMP ?
« on: 18/07/2008 18:54:31 »
Dear Differenceologists,


see this image ?




Nice eh ?

It's only 7k !

Why does the bitmap version weigh in at a hefty 32k for something which looks exactly the same !!..same dimensions etc etc  ?


I want to know, I need to know
I do not know, ewe know !
Help me know , so that I can know
Answer me yes, and don't say no !



Quality poemage yet again !!


Neil
Image Enquirer


xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx






 

Offline DoctorBeaver

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What's The Difference Between a JPEG and a BMP ?
« Reply #1 on: 18/07/2008 19:26:15 »
BMP images aren't compressed, JPGs are. It's the same with AVI and MPEG or WMV, and WAV and MP3.
 

Offline RD

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What's The Difference Between a JPEG and a BMP ?
« Reply #2 on: 18/07/2008 19:34:23 »
The jpeg and the bmp may look the same, but if you subtract one image from the other you will see where detail has been lost in the compressed jpeg (and jpeg artifacts).  If the images were identical subtracting one from the other should produce a blank black screen.
« Last Edit: 18/07/2008 19:44:23 by RD »
 

Offline DoctorBeaver

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What's The Difference Between a JPEG and a BMP ?
« Reply #3 on: 18/07/2008 19:58:35 »
RD - don't be wicked. Poor Sheepy has only just mastered painting by numbers. Now you're telling him about subtraction using images!  :D
 

Offline RD

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What's The Difference Between a JPEG and a BMP ?
« Reply #4 on: 18/07/2008 20:22:46 »
I have exaggerated the contrast and brightness of the bmp-jpeg version

 

Offline DoctorBeaver

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What's The Difference Between a JPEG and a BMP ?
« Reply #5 on: 18/07/2008 20:30:08 »
Show off  :P
 

Offline BenV

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What's The Difference Between a JPEG and a BMP ?
« Reply #6 on: 18/07/2008 21:30:27 »
This is a very basic description, but should give you the idea...

A bitmap is a map of all the bits - in the file it says:

This pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
the next pixel is this colour
and so on...

A jpeg (which stands for Joint Photographic Experts Group - the people who developed it - just like Motion Pictures Expert Group MPEG video) instead says
The first 12 pixes are this colour
The next 20 pixels are this colour...

And so can save all the same info in a smaller file.
 

Offline rosalind dna

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What's The Difference Between a JPEG and a BMP ?
« Reply #7 on: 18/07/2008 21:35:39 »
What is a Bitmap in the difference to Jpeg and the other photographic or technical picture abbreviation that I have forgotten right now.
 

Offline DoctorBeaver

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What's The Difference Between a JPEG and a BMP ?
« Reply #8 on: 18/07/2008 22:01:03 »
If you want the best, scalable graphics format then you need vector graphics rather than raster graphics.
 

paul.fr

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What's The Difference Between a JPEG and a BMP ?
« Reply #9 on: 18/07/2008 22:06:21 »
If you want the best, scalable graphics format then you need vector graphics rather than raster graphics.

 [O8)]
Wot you say man?
 

paul.fr

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What's The Difference Between a JPEG and a BMP ?
« Reply #10 on: 18/07/2008 22:17:18 »
What is a Bitmap in the difference to Jpeg and the other photographic or technical picture abbreviation that I have forgotten right now.

Eh!
 

Offline DoctorBeaver

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What's The Difference Between a JPEG and a BMP ?
« Reply #11 on: 18/07/2008 22:20:02 »
If you want the best, scalable graphics format then you need vector graphics rather than raster graphics.


 [O8)]
Wot you say man?

I was REEFERing to the quality
 

Offline DoctorBeaver

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What's The Difference Between a JPEG and a BMP ?
« Reply #12 on: 18/07/2008 22:21:03 »
What is a Bitmap in the difference to Jpeg and the other photographic or technical picture abbreviation that I have forgotten right now.

Eh!

 

paul.fr

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What's The Difference Between a JPEG and a BMP ?
« Reply #13 on: 18/07/2008 22:23:08 »


I was REEFERing to the quality

Wouldn't you have thought that the different developers would have got together on some sort of JOINT venture, to simplify things?
 

Offline DoctorBeaver

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What's The Difference Between a JPEG and a BMP ?
« Reply #14 on: 18/07/2008 22:24:45 »


I was REEFERing to the quality

Wouldn't you have thought that the different developers would have got together on some sort of JOINT venture, to simplify things?

Instead of just HASHing things together?
 

Offline rosalind dna

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What's The Difference Between a JPEG and a BMP ?
« Reply #15 on: 19/07/2008 00:30:57 »


I was REEFERing to the quality

Wouldn't you have thought that the different developers would have got together on some sort of JOINT venture, to simplify things?

Instead of just HASHing things together?

Dr Beaver thanks for the good explanation and I have a good digital Sony camera not a really technical one but it takes clear photos with Jpeg images. Like the ones of my cats that I posted.
 

lyner

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What's The Difference Between a JPEG and a BMP ?
« Reply #16 on: 19/07/2008 00:48:25 »
JPEG is fine when you choose the appropriate quality for your desired display size. The problem with JPEG files is when you start to edit them. If you want to change the colour, gamma and sharpness (etc) the editor has, first, to change to a bitmap then change things then go back to JPEG. Some of the original 'artifacts' caused by the first JPEG coding get changed by the editing and, when re-JPEG'd, they can look worse than their original, acceptable level. Even just cropping the picture can mess things up.
RAW format is a compression system which avoids artifacts and makes image processing much safer. It takes a lot more memory, though, and means that your memory card cannot store anything like as many images. There are, unfortunately, a lot of different RAW formats and you need to translate them all into a suitable editable format (bitmap).
To see the effects of JPEG compression, look in the fine detail of your sharpest pictures and you will see spidery patterns all over - particularly when you use the highest compression. If you enlarge small portions of an original, they will show up on 'good' prints.
 

Offline Karen W.

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What's The Difference Between a JPEG and a BMP ?
« Reply #17 on: 20/07/2008 12:06:52 »
I have exaggerated the contrast and brightness of the bmp-jpeg version





OH Shame on you RD...NOooooooo... How did you get Neily's Veronica into the general science forum... Oh Poor Neily.. Veronicas two timing you!!  LOL!
 

Offline RD

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What's The Difference Between a JPEG and a BMP ?
« Reply #18 on: 20/07/2008 19:55:47 »
In the UK in 1950s/1960s this view of Veronica was also a male hairstyle: a "Duck's Arse" or "D.A.", similar to a "Tony Curtis".
http://www.time.com/time/magazine/article/0,9171,867107-2,00.html
 

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What's The Difference Between a JPEG and a BMP ?
« Reply #18 on: 20/07/2008 19:55:47 »

 

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