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  #51  
Old January 9th 18, 04:39 PM posted to rec.photo.digital
PeterN[_7_]
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Posts: 990
Default thumbnail sizes

On 1/7/2018 10:12 PM, Savageduck wrote:


snip


...but why the need for thumbnails in the first place, or have I missed
something?


Several reasons:

1. They can be used when thumb tacks take up too much space;
2. They are sturdier than thumb tacks


--
PeterN
  #52  
Old January 9th 18, 04:56 PM posted to rec.photo.digital
PeterN[_7_]
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Posts: 990
Default thumbnail sizes

On 1/8/2018 1:26 PM, nospam wrote:
In article , Alfred
Molon wrote:

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.


If you have your own web photo gallery site, you can use ImageMagick to
produce the thumbnails for the pages (I do so).


you 'can', but only if you want to do it the hard way.

numerous apps can automatically create thumbnails and links to the full
size images simply by exporting a web site, and in a variety of
layouts.



And there is not one word of scripting, or line of code in any of them.


--
PeterN
  #53  
Old January 9th 18, 05:30 PM posted to rec.photo.digital
nospam
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Posts: 21,651
Default thumbnail sizes

In article , PeterN
wrote:

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.

If you have your own web photo gallery site, you can use ImageMagick to
produce the thumbnails for the pages (I do so).


you 'can', but only if you want to do it the hard way.

numerous apps can automatically create thumbnails and links to the full
size images simply by exporting a web site, and in a variety of
layouts.


And there is not one word of scripting, or line of code in any of them.


correct.
  #54  
Old January 12th 18, 06:02 PM posted to rec.photo.digital
Phillip Helbig[_2_]
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Posts: 25
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?

  #55  
Old January 12th 18, 06:05 PM posted to rec.photo.digital
Phillip Helbig[_2_]
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Posts: 25
Default thumbnail sizes

In article , "Carlos E.R."
writes:

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 :-)


Aspect ratio is the same.

  #56  
Old January 12th 18, 06:07 PM posted to rec.photo.digital
Phillip Helbig[_2_]
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Posts: 25
Default thumbnail sizes

In article .com,
Savageduck writes:

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?


To put them on a web page which loads fast with links to
higher-resolution images.

I didn't mention that because I don't see why it's relevant.

Yes, different cameras, but same aspect ratio. Yes, the contents of the
photos are different, but the difference in file size depending on
content is much less than the difference between the two cameras. JPEG
quality is certainly not exactly the same for the high-resolution
images.

  #57  
Old January 12th 18, 06:12 PM posted to rec.photo.digital
Phillip Helbig[_2_]
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Posts: 25
Default thumbnail sizes

In article , "Carlos E.R."
writes:

Maybe he wants to have a directory that loads and browses fast with
small versions of the photos. Who knows?


Right.

For instance, somebody I knew generated them in order to create a web
page on his home server.


Right.

The user would see a bunch of photos, click on
one and get the large version.


Right.

So he wanted to generate much smaller
versions to optimize load time for the preview.


Right.

Yeah, sure, there will be some product out there that does it all. Where
is the joy in it, instead of doing it yourself completely? Or maybe he
was creating one of those "products" :-P


The script will produce thumbnails of an arbitrarily large number of
files. I have another script which produces a complete web page. I
type two commands and it is done. The quality of the thumbnails is not
an issue.

Between the lines, there are some suggestions that some cameras might
somehow include a thumbnail in the JPEG image, which could perhaps be
extracted with less effort than creating a new one with my script. If
so, that would be interesting to know.

Out of curiosity, the question about the different sizes of the
thumbnail files remains, though.

  #58  
Old January 12th 18, 06:45 PM posted to rec.photo.digital
nospam
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Posts: 21,651
Default thumbnail sizes

In article , Phillip Helbig (undress to
reply) 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?


To put them on a web page which loads fast with links to
higher-resolution images.

I didn't mention that because I don't see why it's relevant.


it's very relevant. you're doing things the hard way.

with the proper software, it's a couple of clicks to export a complete
web page (even uploading it to your server), including thumbnails,
links to full size images and in whatever layout you want.

the computer is there to do work *for* you.
  #59  
Old January 12th 18, 06:46 PM posted to rec.photo.digital
Mayayana
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Posts: 1,505
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"Phillip Helbig (undress to reply)" wrote

| 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 :-)
|
| Aspect ratio is the same.
|

Then the only other thing I can think of is that
the cameras are saving at different quality levels
and IM is copying them. Their docs say that's what
it tries to do: Set quality at the same level as it
was saved when possible. You could test it by
setting the quality. That might be a good idea,
anyway. If the camera saved at, say, 90, then
IM is going to save a 90 version of a 90.
You can also just check the quality setting of
the cameras, or the resulting photos. Many viewers
will show the quality level of the last save.

I wrote myself a VBScript to extract thumbnails.
I also wrote an HTA (using an Internet Explorer window)
to show images as thumbnails and click one to
view it larger. That won't do you any good on
Linux, but the idea might be adaptable if you're doing
this locally. It wasn't clear to me whether you're
dynamically loading them to view on your computer
or just creating them once for a website.

If it's local, you may not need to resize at
all. IE (and presumably other browsers) is amazingly
fast and efficient at resizing for display. If you
generate a webpage with:
IMG SRC="D:\bigpic.jpg" WDITH=105 HEIGHT=70
you can very quickly generate a thumbnail sheet
dynamically from full-size images.
Of course you wouldn't want to do it that way
online because it would be slow and your visitors
would need to download the big version.

In case it's useful, here's the thumbnail extractor
package:
http://www.jsware.net/jsware/scrfiles.php5#jpginf

It could probably run in WINE. You just drop a
folder onto it and all available thumbnails are
extracted. But I wouldn't bee surprised if there's
a Linux tool to do the same thing.

And here's the thumbnail viewer:

http://www.jsware.net/jsware/scrfiles.php5#picview

Sample pics he

http://www.jsware.net/jsware/linkpics/tview1a.jpg
http://www.jsware.net/jsware/linkpics/tview2.jpg


  #60  
Old January 13th 18, 10:06 AM posted to rec.photo.digital
Phillip Helbig[_2_]
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Posts: 25
Default thumbnail sizes

In article , "Mayayana"
writes:

Then the only other thing I can think of is that
the cameras are saving at different quality levels
and IM is copying them. Their docs say that's what
it tries to do: Set quality at the same level as it
was saved when possible. You could test it by
setting the quality. That might be a good idea,
anyway. If the camera saved at, say, 90, then
IM is going to save a 90 version of a 90.
You can also just check the quality setting of
the cameras, or the resulting photos. Many viewers
will show the quality level of the last save.


OK. At first glance, it seems that the smaller thumbnail files are from
the camera with higher-quality JPEGs.

If it's local, you may not need to resize at
all. IE (and presumably other browsers) is amazingly
fast and efficient at resizing for display. If you
generate a webpage with:
IMG SRC="D:\bigpic.jpg" WDITH=105 HEIGHT=70
you can very quickly generate a thumbnail sheet
dynamically from full-size images.
Of course you wouldn't want to do it that way
online because it would be slow and your visitors
would need to download the big version.


Right.

In case it's useful, here's the thumbnail extractor
package:
http://www.jsware.net/jsware/scrfiles.php5#jpginf

It could probably run in WINE. You just drop a
folder onto it and all available thumbnails are
extracted. But I wouldn't bee surprised if there's
a Linux tool to do the same thing.


Does this imply that the JPEG files already contain thumbnails?

 




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