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| author | David Barts <n5jrn@me.com> |
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| date | Sun, 26 Jul 2020 15:14:03 -0700 |
| parents | 6b300da7d800 |
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5 <title>Introducing JpegWasher</title> |
| 16 | 6 <style> |
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| 29 | 13 <h1>Introducing JpegWasher</h1> |
| 16 | 14 <h2>Executive Summary</h2> |
| 15 <p>This program makes it easy to remove metadata from the digital images you | |
| 16 create.</p> | |
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17 <h2>What is “Metadata,” and Why Would I Want to Remove It?</h2> |
| 16 | 18 <p>You may not realize it, but image files can (and typically do!) contain |
| 19 more than just image data. These data can include your camera make, model, | |
| 20 and serial number; the location where you took the photo; the software you | |
| 21 used to edit the photo (and what editing steps you did); etc.</p> | |
| 22 <p>One of the most powerful uses of photography is to graphically document | |
| 23 things that the wealthy and powerful might wish to remain concealed. The | |
| 24 evils of slavery, child labor, poverty, war, and imperialism have all been | |
| 25 documented photographically, and such photographs have often proved | |
| 26 instrumental in helping to motivate social change.</p> | |
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27 <p>Because of the metadata they contain, digital photographs contain |
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28 evidence which has been used to determine who took them, and in some cases |
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29 to exact retribution against those photographers, who believed they were |
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30 sharing their photos anonymously. JpegWasher makes it easy to see and |
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31 remove the privacy-compromising metadata in your images.</p> |
| 16 | 32 <p>Even if your images are not of such a sensitive nature, that extra data |
| 33 takes up space. It is not uncommon for a 100 KiB image to contain 20 KiB | |
| 34 of metadata in it; if that image is on a web page, that makes for 20 KiB | |
| 35 of wasted network usage each time the image is sent.</p> | |
| 29 | 36 <h2>What Makes JpegWasher Different from Other Metadata Editors?</h2> |
| 16 | 37 <p>Simply put, it is designed to <em>safely</em> remove <em>unimportant</em> |
| 29 | 38 metadata from JPEG files.</p> |
| 16 | 39 <p>There are plenty of general-purpose image metadata editors out there, and |
| 40 these tools can be employed to remove unimportant metadata. The trouble | |
| 41 is, they are not user-friendly: it is up to you, the user, to know which | |
| 42 metadata are unimportant, and to delete it.</p> | |
| 43 <p>There can be literally <em>hundreds</em> of bits of metadata in an | |
| 44 image, and <em>not all are safe to remove</em>. In particular, if you | |
| 45 accidentally remove color-management metadata, computers that don’t handle | |
| 46 images without color-management metadata properly (I’m talking about <em>you</em>, | |
| 47 Apple Computer, Inc.) will display colors that often look all “washed-out” | |
| 48 or otherwise incorrect.</p> | |
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49 <p>There are already plenty of simple-to-use, user-friendly tools out there |
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50 for cleaning the metadata out of image files, but they inevitably delete <em>all</em> |
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51 metadata, resulting in files that often display improperly. Also of |
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52 concern, many of these “tools” are actually online services. If you’re |
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53 concerned about your privacy, why would you trust the images you’re |
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54 processing to some unknown third party, who may be linked somehow to those |
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55 who might want to retaliate against you?</p> |
| 16 | 56 <p>I wrote this program because I wanted there to be a quick, easy way to |
| 57 scrub images before they even left a photographer’s computer and made | |
| 58 their way onto the Internet, and for that program to leave vital metadata | |
| 59 alone, so that the resulting images continue to display properly.</p> | |
| 29 | 60 <h2>JpegWasher Washes More than Just Exif Metadata</h2> |
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61 <p>Exif is the most common type of metadata, but image files commonly |
| 16 | 62 contain compromising XMP or IPTC data, particularly if they have been |
| 29 | 63 edited with a tool like Photoshop. JpegWasher will seamlessly deal with |
| 16 | 64 these kinds of metadata, too. It tries to do as thorough a job as possible |
| 65 of scrubbing possibly compromising metadata from your images.</p> | |
| 29 | 66 <h2>Using JpegWasher</h2> |
| 67 <p>Just double-click on the JpegWasher icon and a main window should open | |
| 16 | 68 up. Either choose the File… Wash from the menu bar, or just drag image |
| 29 | 69 files onto the main JpegWasher image.</p> |
| 70 <p>When JpegWasher opens an image, it displays all the metadata it finds. | |
| 16 | 71 That metadata will be run through an internal whitelist, and any data |
| 72 whose “key” is not found on the whitelist will be automatically selected | |
| 73 for deletion.</p> | |
| 29 | 74 <p>If you disagree with JpegWasher’s decisions, you can check or uncheck the |
| 16 | 75 boxes next to the metadata in question. When you are satisfied with the |
| 76 choice of metadata to be scrubbed, click “Wash” and all offending metadata | |
| 77 will be removed. A dialog will pop up showing the metadata remaining in | |
| 78 the new, washed file.</p> | |
| 29 | 79 <h3>Important: Run JpegWasher Last!</h3> |
| 17 | 80 <p>Most image-editing tools insert telltale bits of metadata into the output |
| 81 they create. Thus, only way you can create a file with the minimum amount | |
| 29 | 82 of metadata in it is to run JpegWasher as the final step in your image |
| 17 | 83 preparation.</p> |
| 29 | 84 <h3>Washing Non-JPEG Images</h3> |
| 85 <p>In short: it’s possible, but it is not recommended unless you <em>really</em> | |
| 86 know what you’re doing.</p> | |
| 87 <p>JpegWasher is called JpegWasher for a reason: it is geared to cleaning | |
| 88 metadata in <em>JPEG</em> files. Different types of images use metadata | |
| 89 differently; metadata that would be extraneous deadwood in a JPEG can be | |
| 90 critical to interpreting other image file formats correctly. JpegWasher’s | |
| 91 built-in whitelist is geared to what must be retained when washing JPEG | |
| 92 images, so <em>careless use of JpegWasher is likely to damage non-JPEG | |
| 93 files.</em> It is for this reason that JpegWasher will warn you if you | |
| 94 attempt to open and wash a non-JPEG file with it.</p> | |
| 16 | 95 <h2>Output Files</h2> |
| 29 | 96 <p>JpegWasher never modifies an existing image file. Instead, it creates a |
| 16 | 97 new file of the same type but with “_washed” appended to its name. For |
| 98 example, processing <code>foo.jpg</code> will create <code>foo_washed.jpg</code>. | |
| 99 By default, the new file will be created in the same directory as the file | |
| 100 being washed.</p> | |
| 29 | 101 <h2>JpegWasher is Configurable</h2> |
| 16 | 102 <p>Both the whitelist and the destination directory for the washed files are |
| 103 user-configurable in the Preferences menu.</p> | |
| 104 <h3>Configuring the Whitelist</h3> | |
| 105 <p>There are two kinds of whitelist entries: those that match an entire | |
| 106 metadata key, and those that match a key prefix. The latter end in an | |
| 107 asterisk. The whitelist is case-sensitive; i.e. the entry <code>exif.image.colormap</code> | |
| 108 <em>will not</em> match the <code>Exif.Image.ColorMap</code> key.</p> | |
| 17 | 109 <h2>That’s about It</h2> |
| 29 | 110 <p>JpegWasher does not, and probably never will, do anything but remove |
| 111 extraneous metadata from JPEG files.</p> | |
| 17 | 112 <p>First, I have no desire to re-invent the wheel. There are already |
| 113 excellent open-source tools like Gimp for image editing, and ExifTool and | |
| 29 | 114 Exiv2 for general-purpose metadata editing (in fact, JpegWasher is built |
| 17 | 115 on top of Exiv2). If you need the functionality of some other tool, |
| 116 download and use it!</p> | |
| 29 | 117 <p>Second (and more importantly), I want JpegWasher to be simple, and |
| 17 | 118 therefore easy to learn and easy to use. The more challenging an |
| 119 information-security tool is to use, the less likely it is to be used | |
| 120 frequently, and the more likely it is that compromising information gets | |
| 121 disclosed.</p> | |
| 16 | 122 </body> |
| 123 </html> |