Bytes in a pixel?

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Hi,

"How mant bytes are used to construct one pixel?"

I got this question from a friend today. My thinking would be that it depends
on resolution of image in determining answer. However, I want to check with
others before passing this on. Any better answers?

TIA,

Conrad

Conrad Weiler
Camp Sherman, Oregon
 
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Conrad Weiler wrote:

> Hi,
>
> "How mant bytes are used to construct one pixel?"
>
> I got this question from a friend today. My thinking would be that it depends
> on resolution of image in determining answer. However, I want to check with
> others before passing this on. Any better answers?

You're right.. It depends on the color depth etc..

http://www.scantips.com/basics1d.html
 
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weil91@aol.com (Conrad Weiler) writes:

> "How mant bytes are used to construct one pixel?"
>
> I got this question from a friend today. My thinking would be that it depends
> on resolution of image in determining answer.

It doesn't depend on resolution. Resolution determines how many pixels
are in an image, not how many bytes construct a pixel.

What your friend is probably trying to figure out is how much storage is
needed for 3MP, 4MP and 5MP cameras. This actually isn't a function of
the number of pixels, thanks to JPEG compression. Cameras vary in how
large a file they store per image. No matter what the camera, you can
store an image for making sharp prints in (on average) about a million
bytes. You can store an image for making what I think are acceptable
prints in (on average) about a quarter of a million bytes. You can
store a quality 640x480 image for emailing and web sharing in about 50
thousand bytes.

--

http://ourdoings.com/ Let your digital photos organize themselves.
Sign up today for a 7-day free trial.
 
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In article <20041214075501.08318.00002236@mb-m04.aol.com>,
Conrad Weiler <weil91@aol.com> wrote:
>Hi,
>
>"How mant bytes are used to construct one pixel?"
>
>I got this question from a friend today. My thinking would be that it depends
>on resolution of image in determining answer. However, I want to check with
>others before passing this on. Any better answers?

In 24 bit RGB, it's 3 (24 bits, 8 bits per byte). In 48 bit RGB, it's 6. In
256 colour registered GIFs, it's 1. In B&W 8 bits, it's 1. In 8 bit per
channel CMYK, it's 4. The raw output (after decompression) from a Canon DSLR
uses 1.5, etc. etc.
 
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Conrad Weiler wrote:
> Hi,
>
> "How mant bytes are used to construct one pixel?"
>
> I got this question from a friend today. My thinking would be that it depends
> on resolution of image in determining answer. However, I want to check with
> others before passing this on. Any better answers?
>
> TIA,
>
> Conrad
>
> Conrad Weiler
> Camp Sherman, Oregon

It depends on color depth but as Bill says, for the VAST majority of
Cameras, the color depth is 3 bytes per pixel (8 bits/byte).
One byte for Red, one for Green and one for Blue.
By combining the various shades of RGB you get the "true" color of the
pixel.
Bob Williams
 
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It has nothing to do with resolution. Resolution is how many pixels you
have, not how big the pixels are.

If the image is only black and white, no gray, then 8 pixels to 1 byte.

If the image is 8-bit black-and-white (256 shades of gray), 1 byte per
pixel.

If the image is 8-bit color (256 levels each of red, green, and blue), 3
bytes per pixel.

If the image is 16-bit black-and-white or color, twice the above.

File compression, however, makes it possible to store an image in a file
whose size is smaller than what you calculate above. TIFF and ZIP files use
lossless compression; you recover the entire value of every pixel. (They
use concise codes to deal with repeated pixels, which are common, especially
in poster-like images.) JPEG files use lossy compression; they discard some
low-contrast detail in order to get a smaller file.
 
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>From: weil91@aol.com (Conrad Weiler)

>"How mant bytes are used to construct one pixel?"
>
>I got this question from a friend today. My thinking would be that it depends
>on resolution of image in determining answer. However, I want to check with
>others before passing this on. Any better answers?

Ranges from one bit (not byte, bit) for black/white (not grayscale) to 64 bits
(8 bytes) for 16 bit/channel CMYK, so it depends on the mode and color depth
....

Most common is probably 3 bytes for 8 bit/channel RGB files though.
 
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weil91@aol.com (Conrad Weiler) writes:

> Hi,
>
> "How mant bytes are used to construct one pixel?"
>
> I got this question from a friend today. My thinking would be that it depends
> on resolution of image in determining answer. However, I want to check with
> others before passing this on. Any better answers?

one? one and a half? two? three? four and a half? six? eight? This is
where things start getting very complicated. Are you chasing a real
explanation or a 'lies to children' type glib one?

one. 8 bits per pixel in some formats, unusual.

one and a half. If you count the elements in a bayer map of 12 bits
depth sensors and the numbers of final pixels, then this is what you
end up with.

two. Deeper bit depth pixels, usually people align 12 bits into two
bytes, so that's where this come from.

three. Nominal 8 bits, three channels, JPEG levels (apart from all the
wonderful compression, which we won't go into here). You tend to get 3
colocated samples in something like a scanner, so this is valid.

four and a half. 12 bits per channel, packed tightly. Scanner, typically.

six. 16 bits per channel, or 12 bits per channel packed
loosely. Mostly from scanners, really.

eight. 16 bits in four channels. RGB + IR and the IR used to assist
the reconstruction of the other channels. Nikon scanners with ICE etc.

Aren't you sorry you asked?

B>

ps. Compression breaks this horribly and should probably be ignored at
this point.
 
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In article <20041214075501.08318.00002236@mb-m04.aol.com>,
weil91@aol.com (Conrad Weiler) wrote:

> Hi,
>
> "How mant bytes are used to construct one pixel?"
>
> I got this question from a friend today. My thinking would be that it depends
> on resolution of image in determining answer. However, I want to check with
> others before passing this on. Any better answers?
>
> TIA,
>
> Conrad
>
> Conrad Weiler
> Camp Sherman, Oregon

It depends on the source and the storage format. Consider a Bayer
pattern camera that saves as a JPEG. Such a pixel may come from a 12
bit sample of one color, be scaled to 9 bits through gamma correction,
be upsampled using neighboring color data, translated to 8 bit channels
of RGB, converted to YUV, downsampled to Y/1 U/2 V/2 resolution, and
then converted to 2D frequency data of the YUV with different qualities
per channel. Now reverse part of that to get RGB.

How many bits now? It's anybody's guess. Each JPEG output pixel is
represented with 24 bits but much of that information was taken
neighboring pixels rather than a unique 24 bit source. A 640x480 image
from the sample data path above has 640x480x24 bits but it could not
represent 2^(640x480x24) possible combinations.

Confused?
 
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The day you can measure a pixel will be the day I get my mars shuttle seat
booked..


"Conrad Weiler" <weil91@aol.com> wrote in message
news:20041214075501.08318.00002236@mb-m04.aol.com...
> Hi,
>
> "How mant bytes are used to construct one pixel?"
>
> I got this question from a friend today. My thinking would be that it
depends
> on resolution of image in determining answer. However, I want to check
with
> others before passing this on. Any better answers?
>
> TIA,
>
> Conrad
>
> Conrad Weiler
> Camp Sherman, Oregon
 
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"Ryadia" <ryadia@hotmail.com> writes:

> The day you can measure a pixel will be the day I get my mars shuttle seat
> booked..

You seem somewhat hazy on the definition of 'pixel'.

B>
 
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In article <20041214112607.06555.00001262@mb-m24.aol.com>,
Bill Hilton <bhilton665@aol.comedy> wrote:
>>From: weil91@aol.com (Conrad Weiler)
>
>>"How mant bytes are used to construct one pixel?"
>>
>>I got this question from a friend today. My thinking would be that it depends
>>on resolution of image in determining answer. However, I want to check with
>>others before passing this on. Any better answers?
>
>Ranges from one bit (not byte, bit) for black/white (not grayscale) to 64 bits
>(8 bytes) for 16 bit/channel CMYK,

You can do even better than that - I've seen bitmap software that uses
double precision floating point RGB channels. 24 *bytes* per pixel, yeah!
 
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"Ryadia" <ryadia@hotmail.com> writes:

> "Bruce Murphy" <pack-news@rattus.net> wrote in message
> news:m2brcwtn42.fsf@greybat.rattus.net...
> > "Ryadia" <ryadia@hotmail.com> writes:
> >
> > > The day you can measure a pixel will be the day I get my mars shuttle
> seat
> > > booked..
> >
> > You seem somewhat hazy on the definition of 'pixel'.
> >
>
> Perhaps Bruce, you could enlighten us as to the definition?

A discrete element of a planar space, usually rectangular. This isn't
complicated.

B>
 
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On 15 Dec 2004 19:54:15 +0800, Bruce Murphy <pack-news@rattus.net>
wrote:

>"Ryadia" <ryadia@hotmail.com> writes:
>
>> "Bruce Murphy" <pack-news@rattus.net> wrote in message
>> news:m2brcwtn42.fsf@greybat.rattus.net...
>> > "Ryadia" <ryadia@hotmail.com> writes:
>> >
>> > > The day you can measure a pixel will be the day I get my mars shuttle
>> seat
>> > > booked..
>> >
>> > You seem somewhat hazy on the definition of 'pixel'.
>> >
>>
>> Perhaps Bruce, you could enlighten us as to the definition?
>
>A discrete element of a planar space, usually rectangular. This isn't
>complicated.

you mean that's the definition of a sensel on a sensor ? :)
 
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imbsysop <imbsysop@yahoo.com> writes:

> On 15 Dec 2004 19:54:15 +0800, Bruce Murphy <pack-news@rattus.net>
> wrote:
>
> >"Ryadia" <ryadia@hotmail.com> writes:
> >
> >> Perhaps Bruce, you could enlighten us as to the definition?
> >
> >A discrete element of a planar space, usually rectangular. This isn't
> >complicated.
>
> you mean that's the definition of a sensel on a sensor ? :)

No, I don't. A pixel is an abstract concept for which there are many
physical realisations with varying levels of divergence from this
original definition..

B>
 
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"Bruce Murphy" <pack-news@rattus.net> wrote in message
news:m2brcwtn42.fsf@greybat.rattus.net...
> "Ryadia" <ryadia@hotmail.com> writes:
>
> > The day you can measure a pixel will be the day I get my mars shuttle
seat
> > booked..
>
> You seem somewhat hazy on the definition of 'pixel'.
>

Perhaps Bruce, you could enlighten us as to the definition?
 
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Conrad Weiler wrote:

> Hi,
>
> "How mant bytes are used to construct one pixel?"
>
> I got this question from a friend today. My thinking would be that it depends
> on resolution of image in determining answer. However, I want to check with
> others before passing this on. Any better answers?
>
> TIA,
>
> Conrad
>
> Conrad Weiler
> Camp Sherman, Oregon

It depends on the colour depth of the image.
Assuming that a byte is 8 bits, then:
48 bit colour depth is 6 bytes per pixel
32 bit colour depth is 4 bytes per pixel.
24 bit colour depth is 3 bytes per pixel.
16 bit colour depth is 2 byte per pixel.
8 bit colour depth is 1 byte per pixel.

This is directly related to a bitmap (uncompressed) image file size.
A 4Mp image at 48 bit colour is 192 MB (Mega Bytes).
The same image at 32 bit colour is 128 MB.
Again, at 24 bit colour, it is 96 MB.
....And so on, and so forth.
 
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In article <psadncMkpe8naV3cRVn-1A@comcast.com>, Paul H.
<xxpaulhtck@zzcomcast.yycom> writes
>
>"Bruce Murphy" <pack-news@rattus.net> wrote in message
>news:m23by7nl4h.fsf@greybat.rattus.net...
>> "Paul H." <xxpaulhtck@zzcomcast.yycom> writes:
>>
>> [ snip my spatial definition of pixel and ryadia's incapactity to grasp
>it ]
>>
>> > Here's a simple definition: a pixel is an ordered 3-tuple in a
>> > three-dimensional color space having equal bit resolution along each
>> > orthogonal color axis. Given Nb as the number of bits of resolution
>along
>> > each color axis, where Nb for practical purposes is limited by the
>> > expression Nb>=8, the number of bytes per pixel, Bpp, is given by
>>
>> Unfortunately what you've defined is (one of several possible) a
>> colour representation for a pixel rather than a pixel itself.
>
>It was also meant to be completely in jest. Thanks for picking up on that.
>
As a gnatsarseologist myself, I must say I'm disappointed.
--
Roger Hunt
 
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"Paul H." <xxpaulhtck@zzcomcast.yycom> writes:

[ snip my spatial definition of pixel and ryadia's incapactity to grasp it ]

> Here's a simple definition: a pixel is an ordered 3-tuple in a
> three-dimensional color space having equal bit resolution along each
> orthogonal color axis. Given Nb as the number of bits of resolution along
> each color axis, where Nb for practical purposes is limited by the
> expression Nb>=8, the number of bytes per pixel, Bpp, is given by

Unfortunately what you've defined is (one of several possible) a
colour representation for a pixel rather than a pixel itself.

B>
 
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"Bruce Murphy" <pack-news@rattus.net> wrote in message
news:m23by7nl4h.fsf@greybat.rattus.net...
> "Paul H." <xxpaulhtck@zzcomcast.yycom> writes:
>
> [ snip my spatial definition of pixel and ryadia's incapactity to grasp
it ]
>
> > Here's a simple definition: a pixel is an ordered 3-tuple in a
> > three-dimensional color space having equal bit resolution along each
> > orthogonal color axis. Given Nb as the number of bits of resolution
along
> > each color axis, where Nb for practical purposes is limited by the
> > expression Nb>=8, the number of bytes per pixel, Bpp, is given by
>
> Unfortunately what you've defined is (one of several possible) a
> colour representation for a pixel rather than a pixel itself.

It was also meant to be completely in jest. Thanks for picking up on that.
 
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