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Extract data from a photo

October3

All pictures taken with digital cameras add information to images they take. A lot of information. To see it, install imagemagick using this command on the command line..

sudo apt-get install imagemagick

Then, just use the identify command thus..

identify -verbose /home/me/pics/some_picture.jpg

and it should pump out a heap of data.

Personally, if ever uploading photos to the internet (never) or emailing them to friends (rarely), I make sure to strip all the data from them. For this, use mogrify, also from the imagemagick suite…

mogrify -strip /home/me/pics/some_picture.jpg

Now the exif data has been removed. Nice!

 

True dat..

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Convert .JPGs to PDFs

September5

Sometimes you need to take a pic of a document say, and then put it into a pdf. Here’s how. In Linux.

You’ll need the awesome imagemagick package first. To install it, use..

sudo apt-get install imagemagick

Once that’s in, open a terminal window. Navigate to the folder you have the images in and then just run the command…

convert the_image.jpg the_document.pdf

Got multiple JPGs and need to squeeze all the images into the same pdf?

convert *.jpg the_document.pdf

Need to reduce the images to 1024 pixels across by whatever down and strip out meta data in the JPG files first though? Fer security and confidentiality?

mogrify -strip -resize 1024x *.JPG

“Nice one centurion, Like it.”

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How do I downsize a Hi-Def movie?

August22

In Debian / Ubuntu, use avconv.

avconv -i input.mp4 -b 64k -s hd720 -strict experimental output.mp4

This command uses avconv, where..

-i input.mp4 = the input file name
-b 64k = down sample the audio channel to 64k – should be fine.
-s hd720 = reduce the video from hd1020 to the 720 format
-strict experimental = Allows mp4 output
output.mp4 = the output file.

If you haven’t got avconv installed, use

sudo apt-get install avconv

and follow instructions.

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How do I quickly process photos for upload to the internet?

August21

In Linux, the easiest way to process images is using imagemagick. It is a command line program you can use to manipulate images very quickly. With it, you can scale images, adjust proportions, add watermarks and alot lot more.

These days, with photos from your camera tpyically of the order of 1.2 – 2.5MB in size, uploading them to the internet in bulk is the stuff of dreams, so better to scale them all down and then upload. Here’s how.

Step 1. Install imagemagick.

Open a terminal window using CTRL + ALT + T

Now, install imagemagik..

sudo apt-get install imagemagik

Now let’s try some examples…

First off, copy the photos you want to modify to a new folder, so you have the originals intact, otheriwse you will modify the originals. Bad idea.

We’ll call this folder /home/darth/pics in these examples.

Reduce the photo called hoth.jpg by 50%

mogrify -resize 50% /home/darth/pics/hoth.jpg

Scale the image to be 1024 pixels wide and whatever number of pixels high, scaled in proportion…

mogrify -resize 1024x /home/darth/pics/hoth.jpg

Scale the image to be 500 pixels high and whatever number of pixels wide, scaled in proportion…

mogrify -resize x500 /home/darth/pics/hoth.jpg

Strip the image of all exif data, so remove make and model of camera, GPS data, flash, shutter and aperture speed, etc. etc.

mogrify -strip /home/darth/pics/hoth.jpg

Do the whole freakin’ folder! (Rotate the photos as required, reize them to be 1024 pixels across the top and do that for all jpegs in the folders and subfolders in /home/darth/pics/deathstar

mogrify --auto-orient -strip -resize 1024x /home/darth/pics/deathstar/*/*.JPG

There are a bajillion more possibilities and commands and options in the suite. Check it out. http://www.imagemagick.org/script/command-line-tools.php

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I used to run Click Technology from 1995 to 2010.  Now no longer, I maintain the site with things I find interesting or are noteworthy or have some handy-tip value.