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Old December 2nd 18, 01:49 PM posted to rec.photo.digital
Carlos E.R.
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Posts: 278
Default Just What is a Bitmap?

On 01/12/2018 23.45, Neil wrote:
On 12/1/2018 4:18 PM, RichardLamprey wrote:
When someone says "use a jpeg bitmap", what do they mean?

Googling for how to create a jpeg bitmap says it's pretty much anything
https://www.techwalla.com/articles/h...reate-a-bitmap

Microsoft thinks a jpeg bitmap is something specific
https://docs.microsoft.com/en-us/dot...ap-at-run-time


Artists maybe create jpeg bitmaps by hand?
https://magazine.art21.org/2011/09/1.../#.XAL5P9NOk4k


Programmers maybe create jpeg bitmaps from text files?
https://social.msdn.microsoft.com/Fo...ng-a-text-file


Diehards even seem to be using hex editors to make jpeg bitmaps
https://www.quora.com/How-can-I-make...g-a-hex-editor


I'm not asking about bmp file format but about bitmaps in jpeg format.
What is a bitmap jpeg file anyways?

Perhaps it would help to separate the two terms. To answer the general
question, a 'bitmap' is an image comprised of squares arranged in rows
and columns.

JPEG is a file format that contains a version of the original bitmap
image and organizes aspects of the image such as its resolution relative
to the original, file size and other factors. One original purpose of
the jpeg format was to allow journalist photographers to send images
across the internet when 300bps modems were commonplace.


I'm unsure a jpeg can be considered a format usable for bitmap
manipulation, because it is a lossy format. So someone creating or
changing a bitmap would not use jpeg because individual pixels can
change or just be lost. A bunch of spatially contiguous pixels can be
grouped and get the same value - when in the original they were different.

--
Cheers, Carlos.