thumbnail sizes
 

On 2018-01-07 23:30, 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
|
| 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.)

Oh, I'm more than 95% certain :-)


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.

I rather suppose he is curious about why they are not about the same
size, if the pixel number is the same.

But it does not matter to me why is he making them. Not my business :-)

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

It is a perfectly suited tool for this task (a repeated task in a script).

much care about the quality of them. But you
do care about the file size? Why?

Then use the -quality parameter, to make sure it is the same on all
runs. With no value given, the program tries to estimate the value used
in the original and use the same (see
http://www.imagemagick.org/script/co...s.php#quality).

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

Sigh... Maybe he doesn't know what other information to provide, and
you can simply politely ask for what you think you need :-)


--
Cheers, Carlos.

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

thumbnail sizes
 

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

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?

Why use “convert� which I have never heard of when I have Lightroom,
Bridge, and a few others in my photgraphic tool box?

--

Regards,
Savageduck

thumbnail sizes
 

On 2018-01-08 03:14, Savageduck wrote:
On Jan 7, 2018, Carlos E.R. wrote
(in article ):


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?

Does it matter?

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.

Yes, you do. Any JPG generation has a "quality". It can be "one", so
very bad, or it can be "a hundred", so as best as can be, or any number
in between. Any jpg generated or changed has a quality number. You
choose the number, or you let the software decide.

Having a quality does not mean having high quality.


--
Cheers, Carlos.

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.

thumbnail sizes
 

In article , Carlos E.R.
wrote:


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?

Does it matter?

yes.

If there is some odd reason to produce them, which has yet to be explained,
why would the concept of ³quality² 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.

Yes, you do. Any JPG generation has a "quality". It can be "one", so
very bad, or it can be "a hundred", so as best as can be, or any number
in between. Any jpg generated or changed has a quality number. You
choose the number, or you let the software decide.

that doesn't answer the question.

thumbnail sizes
 

In article , Carlos E.R.
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

Why?
Why not use decent software?

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

there's no need to use a script at all. why make things more difficult
than they need to be?

thumbnail sizes
 

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

On 2018-01-08 03:14, Savageduck wrote:
On Jan 7, 2018, Carlos E.R. wrote
(in ):

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?

Does it matter?

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.

Yes, you do. Any JPG generation has a "quality". It can be "one", so
very bad, or it can be "a hundred", so as best as can be, or any number
in between. Any jpg generated or changed has a quality number. You
choose the number, or you let the software decide.

Having a quality does not mean having high quality.

....er, OK. It seems we are talking at cross purposes. While I have produced
many JPEGs, I have not gone out of my way to deliberately produce thumbnails.

--

Regards,
Savageduck

thumbnail sizes
 

On 2018-01-08 03:17, Savageduck wrote:
On Jan 7, 2018, Carlos E.R. wrote
(in article ):

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?

Why use “convert� which I have never heard of when I have Lightroom,
Bridge, and a few others in my photgraphic tool box?

Because it is a tool designed for scripts and other repetitive tasks.
Most Linux users doing image handling will be familiar with it, but you
also have it in Windows, and is used by other tools in the back without
telling you.

https://en.wikipedia.org/wiki/ImageMagick


The tiny code excerpt from the OP would process an entire directory in
one click. Or one "enter". As you can see in the documentation,
"convert" has dozens of possible options, several pages:

http://imagemagick.org/script/convert.php

There are also many examples of use. For instance, there is one
"-thumbnail":

https://www.imagemagick.org/Usage/resize/#thumbnail


A whole chapter of it:

https://www.imagemagick.org/Usage/thumbnails/


And it has some information that may explain what is happening to the OP:

«Many images from digital cameras, scanning software, and some paint
programs (photoshop is notorious for this), save extra information about
the image in the form of profiles. This includes image formats such a
JPEG, PNG, TIFF and as of IM v6.2.4-1 GIF. Of course the IM specific
format, MIFF also does this. (See Image Profiles for more detailed
information).»

«These profiles can be up to 60 Kb in size, so can make a big difference
to your file size, and by default IM will preserve this profile
information. Thumbnails have no need for this data and often not even
the main image needs it.»


--
Cheers, Carlos.

thumbnail sizes
 

On 2018-01-08 03:49, nospam wrote:
In article , Carlos E.R.
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

Why?
Why not use decent software?

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

there's no need to use a script at all. why make things more difficult
than they need to be?

Scripts are trivial to use for automation. What, you do not know...? Wow.

--
Cheers, Carlos.