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-   -   thumbnail sizes (http://www.photobanter.com/showthread.php?t=131076)

Phillip Helbig[_2_] January 7th 18 09:07 PM

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.


Mayayana January 7th 18 09:46 PM

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.



Carlos E.R. January 7th 18 10:01 PM

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.

Carlos E.R. January 7th 18 10:03 PM

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.

Savageduck[_3_] January 7th 18 10:22 PM

thumbnail sizes
 
On Jan 7, 2018, Phillip Helbig (undress to reply wrote
(in article ):

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


Why?
Why not use decent software?

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?


Different cameras, different image content.

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.


The RAW file size, and native JPEG size is going to be different for those
two cameras. As a result any thumbnail from those different sources is going
to have a different size.

I am still curious as to why you need to generate thumbnails. It seems to be
a pointless exercise.

--

Regards,
Savageduck


Savageduck[_3_] January 7th 18 10:26 PM

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


Mayayana January 7th 18 11:17 PM

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.




Mayayana January 7th 18 11:30 PM

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
|
| 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.
|

Are the originals the same aspect ratio?
If not then you might be getting something
like a 105x65 and a 105x50. You also didn't
spec the compression level with the quality
parameter. (Assuming you're using ImageMagick
as Carlos speculated.)

You didn't say what the context of the code
is. You didn't say why you're making thumbnails
or whether they need to be the same size. You
didn't extract them, which would probably make
more sense. So all we know is that you're making
thumbnails with a poorly suited tool and you don't
much care about the quality of them. But you
do care about the file size? Why?

It'd be easier for people to provide a helpful
answer if you'd explain yourself. We're not your
mother.



Carlos E.R. January 8th 18 02:33 AM

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.

Carlos E.R. January 8th 18 02:39 AM

thumbnail sizes
 
On 2018-01-07 22:22, Savageduck wrote:
On Jan 7, 2018, Phillip Helbig (undress to reply wrote
(in article ):

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


Why?
Why not use decent software?


"convert" is very decent and powerful software.
What would you use in a script, then?

--
Cheers, Carlos.


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