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  #1  
Old January 7th 18, 09:07 PM posted to rec.photo.digital
Phillip Helbig[_2_]
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Posts: 30
Default thumbnail sizes

I've been using this to make thumbnails of jpeg files:

for img in *.JPG; do
echo thumbnailing $img
convert -geometry 105x70 $img $img
done

Files from the K10D result in thumbnails of about 57 kB and those from
the GR of about 46 kB, with little variation. Is there a simple
explanation as to why?

The K10D is 10 megapixels and the GR 16, but I don't see why that is
relevant here, but maybe I am missing something.

  #2  
Old January 7th 18, 09:46 PM posted to rec.photo.digital
Mayayana
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Posts: 1,514
Default thumbnail sizes

"Phillip Helbig (undress to reply)" wrote

| I've been using this to make thumbnails of jpeg files:
|
| for img in *.JPG; do
| echo thumbnailing $img
| convert -geometry 105x70 $img $img
| done
|

Are people supposed to know what OS/software
you're using that code with?

I wonder why you don't just extract the thumbnails
when possible. Don't your cameras create them in
the JPGs? It should be quicker and yield better
quality images.


  #3  
Old January 7th 18, 10:01 PM posted to rec.photo.digital
Carlos E.R.
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Posts: 278
Default thumbnail sizes

On 2018-01-07 21:46, Mayayana wrote:
"Phillip Helbig (undress to reply)" wrote

| I've been using this to make thumbnails of jpeg files:
|
| for img in *.JPG; do
| echo thumbnailing $img
| convert -geometry 105x70 $img $img
| done
|

Are people supposed to know what OS/software
you're using that code with?


Linux/bash and ImageMagick, obviously :-P


I wonder why you don't just extract the thumbnails
when possible. Don't your cameras create them in
the JPGs? It should be quicker and yield better
quality images.


To customize the size and quality, for instance.


--
Cheers, Carlos.
  #4  
Old January 7th 18, 10:26 PM posted to rec.photo.digital
Savageduck[_3_]
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Posts: 16,487
Default thumbnail sizes

On Jan 7, 2018, Carlos E.R. wrote
(in article ):

On 2018-01-07 21:46, Mayayana wrote:
"Phillip Helbig (undress to wrote

I've been using this to make thumbnails of jpeg files:

for img in *.JPG; do
echo thumbnailing $img
convert -geometry 105x70 $img $img
done


Are people supposed to know what OS/software
you're using that code with?


Linux/bash and ImageMagick, obviously :-P


That figures.

I wonder why you don't just extract the thumbnails
when possible. Don't your cameras create them in
the JPGs? It should be quicker and yield better
quality images.


To customize the size and quality, for instance.


Quality for thumbnails?
To what purpose?
It seems to be a waste of time, and a futile, unnecessary exercise.

--

Regards,
Savageduck

  #5  
Old January 8th 18, 02:33 AM posted to rec.photo.digital
Carlos E.R.
external usenet poster
 
Posts: 278
Default thumbnail sizes

On 2018-01-07 22:26, Savageduck wrote:
On Jan 7, 2018, Carlos E.R. wrote
(in article ):

On 2018-01-07 21:46, Mayayana wrote:
"Phillip Helbig (undress to wrote

I've been using this to make thumbnails of jpeg files:

for img in *.JPG; do
echo thumbnailing $img
convert -geometry 105x70 $img $img
done

Are people supposed to know what OS/software
you're using that code with?


Linux/bash and ImageMagick, obviously :-P


That figures.

I wonder why you don't just extract the thumbnails
when possible. Don't your cameras create them in
the JPGs? It should be quicker and yield better
quality images.


To customize the size and quality, for instance.


Quality for thumbnails?
To what purpose?
It seems to be a waste of time, and a futile, unnecessary exercise.


No. I said "to customize the size and quality" which is different than
doing a quality thumbnail. ie, to have thumbnails of the exact quality
(small quality) that one wishes.

--
Cheers, Carlos.
  #6  
Old January 8th 18, 03:14 AM posted to rec.photo.digital
Savageduck[_3_]
external usenet poster
 
Posts: 16,487
Default thumbnail sizes

On Jan 7, 2018, Carlos E.R. wrote
(in article ):

On 2018-01-07 22:26, Savageduck wrote:
On Jan 7, 2018, Carlos E.R. wrote
(in article ):

On 2018-01-07 21:46, Mayayana wrote:
"Phillip Helbig (undress to
wrote

I've been using this to make thumbnails of jpeg files:

for img in *.JPG; do
echo thumbnailing $img
convert -geometry 105x70 $img $img
done

Are people supposed to know what OS/software
you're using that code with?

Linux/bash and ImageMagick, obviously :-P


That figures.

I wonder why you don't just extract the thumbnails
when possible. Don't your cameras create them in
the JPGs? It should be quicker and yield better
quality images.

To customize the size and quality, for instance.


Quality for thumbnails?
To what purpose?
It seems to be a waste of time, and a futile, unnecessary exercise.


No. I said "to customize the size and quality" which is different than
doing a quality thumbnail. ie, to have thumbnails of the exact quality
(small quality) that one wishes.


I am still baffled as why these thumbnails have to be produced in the first
place. A proof/contact sheet, some sort of project, what?

If there is some odd reason to produce them, which has yet to be explained,
why would the concept of “quality” be attached to thumbnails of all
things?

I have been doing this digital photography thing for some time, and I have
yet to have the need to produce a thumbnail of any quality.

--

Regards,
Savageduck

  #7  
Old January 8th 18, 03:49 AM posted to rec.photo.digital
nospam
external usenet poster
 
Posts: 24,165
Default thumbnail sizes

In article , Mayayana
wrote:


| I've been using this to make thumbnails of jpeg files:
|
| for img in *.JPG; do
| echo thumbnailing $img
| convert -geometry 105x70 $img $img
| done
|

Are people supposed to know what OS/software
you're using that code with?


yes

I wonder why you don't just extract the thumbnails
when possible. Don't your cameras create them in
the JPGs? It should be quicker and yield better
quality images.


maybe he wants a different size.
  #8  
Old January 12th 18, 07:02 PM posted to rec.photo.digital
Phillip Helbig[_2_]
external usenet poster
 
Posts: 30
Default thumbnail sizes

In article , "Mayayana"
writes:

| I've been using this to make thumbnails of jpeg files:
|
| for img in *.JPG; do
| echo thumbnailing $img
| convert -geometry 105x70 $img $img
| done
|

Are people supposed to know what OS/software
you're using that code with?


No, but it shouldn't be necessary to get the gist of the above.

I wonder why you don't just extract the thumbnails
when possible. Don't your cameras create them in
the JPGs? It should be quicker and yield better
quality images.


Maybe they do; I don't know. How can I check.

For the same size, why should they be better quality?

  #9  
Old January 7th 18, 10:03 PM posted to rec.photo.digital
Carlos E.R.
external usenet poster
 
Posts: 278
Default thumbnail sizes

On 2018-01-07 21:07, Phillip Helbig (undress to reply) wrote:
I've been using this to make thumbnails of jpeg files:

for img in *.JPG; do
echo thumbnailing $img
convert -geometry 105x70 $img $img
done

Files from the K10D result in thumbnails of about 57 kB and those from
the GR of about 46 kB, with little variation. Is there a simple
explanation as to why?

The K10D is 10 megapixels and the GR 16, but I don't see why that is
relevant here, but maybe I am missing something.


I was going to say that the camera with more megapixels would convert to
a bigger size, but the reverse is happening.

--
Cheers, Carlos.
  #10  
Old January 7th 18, 11:17 PM posted to rec.photo.digital
Mayayana
external usenet poster
 
Posts: 1,514
Default thumbnail sizes

"Carlos E.R." wrote

| I was going to say that the camera with more megapixels would convert to
| a bigger size, but the reverse is happening.
|

MP doesn't matter because it's the same
number of pixels in the thumbnail if they're
both the same width/height. There could be
slight differences due to simpler or more complex
images that compress differently, but with such
a big difference the only explanation I can
think of is that there's a difference in the
compression. The code doesn't include a
"quality" parameter to set compression level
so maybe ImageMagick is deciding based on
input size? Who knows? He's using a hammer
to hit a tack.

It's hard to see why it should matter. He's
using a limited command line tool to get
thumbnails and not even setting the quality
option. Does he really need exactly that size?
If so, why? Is it worth sacrificing quality?
He didn't explain any of that. Apparently he
doesn't care very much about the quality but
is just curious about the different file sizes
resulting.



 




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