Mercurial > cgi-bin > hgweb.cgi > JpegWasher

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    <h1>Introducing JpegWasher</h1>
    <h2>Executive Summary</h2>
    <p>This program makes it easy to remove metadata from the digital images you
      create.</p>
    <h2>What is “Metadata” and Why Would I Want to Remove It?</h2>
    <p>You may not realize it, but image files can (and typically do!) contain
      more than just image data. These data can include your camera make, model,
      and serial number; the location where you took the photo; the software you
      used to edit the photo (and what editing steps you did); etc.</p>
    <p>One of the most powerful uses of photography is to graphically document
      things that the wealthy and powerful might wish to remain concealed. The
      evils of slavery, child labor, poverty, war, and imperialism have all been
      documented photographically, and such photographs have often proved
      instrumental in helping to motivate social change.</p>
    <p>Because of the metadata they contain, digital photographs contain data
      which has been used to determine who took them, and in some cases to exact
      retribution against those photographers. JpegWasher makes it easy to see
      and remove the privacy-compromising metadata in your images.</p>
    <p>Even if your images are not of such a sensitive nature, that extra data
      takes up space. It is not uncommon for a 100 KiB image to contain 20 KiB
      of metadata in it; if that image is on a web page, that makes for 20 KiB
      of wasted network usage each time the image is sent.</p>
    <h2>What Makes JpegWasher Different from Other Metadata Editors?</h2>
    <p>Simply put, it is designed to <em>safely</em> remove <em>unimportant</em>
      metadata from JPEG files.</p>
    <p>There are plenty of general-purpose image metadata editors out there, and
      these tools can be employed to remove unimportant metadata. The trouble
      is, they are not user-friendly: it is up to you, the user, to know which
      metadata are unimportant, and to delete it.</p>
    <p>There can be literally <em>hundreds</em> of bits of metadata in an
      image, and <em>not all are safe to remove</em>. In particular, if you
      accidentally remove color-management metadata, computers that don’t handle
      images without color-management metadata properly (I’m talking about <em>you</em>,
      Apple Computer, Inc.) will display colors that often look all “washed-out”
      or otherwise incorrect.</p>
    <p>Likewise, there are already plenty of simple-to-use, user-friendly tools
      out there for cleaning the metadata out of image files, but they
      inevitably delete <em>all</em> metadata, resulting in files that often
      display improperly. Also of concern, many of these “tools” are actually
      online services. If you’re concerned about your privacy, why would you
      trust the images you’re processing to some unknown third party, who may be
      linked somehow to those who might want to retaliate against you?</p>
    <p>I wrote this program because I wanted there to be a quick, easy way to
      scrub images before they even left a photographer’s computer and made
      their way onto the Internet, and for that program to leave vital metadata
      alone, so that the resulting images continue to display properly.</p>
    <h2>JpegWasher Washes More than Just Exif Metadata</h2>
    <p>Jpeg is the most common type of metadata, but image files commonly
      contain compromising XMP or IPTC data, particularly if they have been
      edited with a tool like Photoshop. JpegWasher will seamlessly deal with
      these kinds of metadata, too. It tries to do as thorough a job as possible
      of scrubbing possibly compromising metadata from your images.</p>
    <h2>Using JpegWasher</h2>
    <p>Just double-click on the JpegWasher icon and a main window should open
      up. Either choose the File… Wash from the menu bar, or just drag image
      files onto the main JpegWasher image.</p>
    <p>When JpegWasher opens an image, it displays all the metadata it finds.
      That metadata will be run through an internal whitelist, and any data
      whose “key” is not found on the whitelist will be automatically selected
      for deletion.</p>
    <p>If you disagree with JpegWasher’s decisions, you can check or uncheck the
      boxes next to the metadata in question. When you are satisfied with the
      choice of metadata to be scrubbed, click “Wash” and all offending metadata
      will be removed. A dialog will pop up showing the metadata remaining in
      the new, washed file.</p>
    <h3>Important: Run JpegWasher Last!</h3>
    <p>Most image-editing tools insert telltale bits of metadata into the output
      they create. Thus, only way you can create a file with the minimum amount
      of metadata in it is to run JpegWasher as the final step in your image
      preparation.</p>
    <h3>Washing Non-JPEG Images</h3>
    <p>In short: it’s possible, but it is not recommended unless you <em>really</em>
      know what you’re doing.</p>
    <p>JpegWasher is called JpegWasher for a reason: it is geared to cleaning
      metadata in <em>JPEG</em> files. Different types of images use metadata
      differently; metadata that would be extraneous deadwood in a JPEG can be
      critical to interpreting other image file formats correctly. JpegWasher’s
      built-in whitelist is geared to what must be retained when washing JPEG
      images, so <em>careless use of JpegWasher is likely to damage non-JPEG
        files.</em> It is for this reason that JpegWasher will warn you if you
      attempt to open and wash a non-JPEG file with it.</p>
    <h2>Output Files</h2>
    <p>JpegWasher never modifies an existing image file. Instead, it creates a
      new file of the same type but with “_washed” appended to its name. For
      example, processing <code>foo.jpg</code> will create <code>foo_washed.jpg</code>.
      By default, the new file will be created in the same directory as the file
      being washed.</p>
    <h2>JpegWasher is Configurable</h2>
    <p>Both the whitelist and the destination directory for the washed files are
      user-configurable in the Preferences menu.</p>
    <h3>Configuring the Whitelist</h3>
    <p>There are two kinds of whitelist entries: those that match an entire
      metadata key, and those that match a key prefix. The latter end in an
      asterisk. The whitelist is case-sensitive; i.e. the entry <code>exif.image.colormap</code>
      <em>will not</em> match the <code>Exif.Image.ColorMap</code> key.</p>
    <h2>That’s about It</h2>
    <p>JpegWasher does not, and probably never will, do anything but remove
      extraneous metadata from JPEG files.</p>
    <p>First, I have no desire to re-invent the wheel. There are already
      excellent open-source tools like Gimp for image editing, and ExifTool and
      Exiv2 for general-purpose metadata editing (in fact, JpegWasher is built
      on top of Exiv2). If you need the functionality of some other tool,
      download and use it!</p>
    <p>Second (and more importantly), I want JpegWasher to be simple, and
      therefore easy to learn and easy to use. The more challenging an
      information-security tool is to use, the less likely it is to be used
      frequently, and the more likely it is that compromising information gets
      disclosed.</p>
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author	David Barts <davidb@stashtea.com>
date	Sun, 03 May 2020 17:36:50 -0700
parents	0161374f7a60
children	35fb8de77c7d