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Add documentation in alternative formats to HTML.
author David Barts <davidb@stashtea.com>
date Sat, 18 Apr 2020 09:08:23 -0700
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1 [This file automatically generated by pandoc from 'Readme.html'.]
2
3 Introducing JpegWasher
4 ======================
5
6 Executive Summary
7 -----------------
8
9 This program makes it easy to remove metadata from the digital images
10 you create.
11
12 What is “Metadata” and Why Would I Want to Remove It?
13 -----------------------------------------------------
14
15 You may not realize it, but image files can (and typically do!) contain
16 more than just image data. These data can include your camera make,
17 model, and serial number; the location where you took the photo; the
18 software you used to edit the photo (and what editing steps you did);
19 etc.
20
21 One of the most powerful uses of photography is to graphically document
22 things that the wealthy and powerful might wish to remain concealed. The
23 evils of slavery, child labor, poverty, war, and imperialism have all
24 been documented photographically, and such photographs have often proved
25 instrumental in helping to motivate social change.
26
27 Because of the metadata they contain, digital photographs contain data
28 which has been used to determine who took them, and in some cases to
29 exact retribution against those photographers. JpegWasher makes it easy
30 to see and remove the privacy-compromising metadata in your images.
31
32 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.
36
37 What Makes JpegWasher Different from Other Metadata Editors?
38 ------------------------------------------------------------
39
40 Simply put, it is designed to *safely* remove *unimportant* metadata
41 from JPEG files.
42
43 There are plenty of general-purpose image metadata editors out there,
44 and these tools can be employed to remove unimportant metadata. The
45 trouble is, they are not user-friendly: it is up to you, the user, to
46 know which metadata are unimportant, and to delete it.
47
48 There can be literally *hundreds* of bits of metadata in an image, and
49 *not all are safe to remove*. In particular, if you accidentally remove
50 color-management metadata, computers that don’t handle images without
51 color-management metadata properly (I’m talking about *you*, Apple
52 Computer, Inc.) will display colors that often look all “washed-out” or
53 otherwise incorrect.
54
55 Likewise, there are already plenty of simple-to-use, user-friendly tools
56 out there for cleaning the metadata out of image files, but they
57 inevitably delete *all* metadata, resulting in files that often display
58 improperly. Also of concern, many of these “tools” are actually online
59 services. If you’re concerned about your privacy, why would you trust
60 the images you’re processing to some unknown third party, who may be
61 linked somehow to those who might want to retaliate against you?
62
63 I wrote this program because I wanted there to be a quick, easy way to
64 scrub images before they even left a photographer’s computer and made
65 their way onto the Internet, and for that program to leave vital
66 metadata alone, so that the resulting images continue to display
67 properly.
68
69 JpegWasher Washes More than Just Exif Metadata
70 ----------------------------------------------
71
72 Jpeg is the most common type of metadata, but image files commonly
73 contain compromising XMP or IPTC data, particularly if they have been
74 edited with a tool like Photoshop. JpegWasher will seamlessly deal with
75 these kinds of metadata, too. It tries to do as thorough a job as
76 possible of scrubbing possibly compromising metadata from your images.
77
78 Using JpegWasher
79 ----------------
80
81 Just double-click on the JpegWasher icon and a main window should open
82 up. Either choose the File… Wash from the menu bar, or just drag image
83 files onto the main JpegWasher image.
84
85 When JpegWasher opens an image, it displays all the metadata it finds.
86 That metadata will be run through an internal whitelist, and any data
87 whose “key” is not found on the whitelist will be automatically selected
88 for deletion.
89
90 If you disagree with JpegWasher’s decisions, you can check or uncheck
91 the boxes next to the metadata in question. When you are satisfied with
92 the choice of metadata to be scrubbed, click “Wash” and all offending
93 metadata will be removed. A dialog will pop up showing the metadata
94 remaining in the new, washed file.
95
96 Important: Run JpegWasher Last!
97 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
98
99 Most image-editing tools insert telltale bits of metadata into the
100 output they create. Thus, only way you can create a file with the
101 minimum amount of metadata in it is to run JpegWasher as the final step
102 in your image preparation.
103
104 Washing Non-JPEG Images
105 ~~~~~~~~~~~~~~~~~~~~~~~
106
107 In short: it’s possible, but it is not recommended unless you *really*
108 know what you’re doing.
109
110 JpegWasher is called JpegWasher for a reason: it is geared to cleaning
111 metadata in *JPEG* files. Different types of images use metadata
112 differently; metadata that would be extraneous deadwood in a JPEG can be
113 critical to interpreting other image file formats correctly.
114 JpegWasher’s built-in whitelist is geared to what must be retained when
115 washing JPEG images, so *careless use of JpegWasher is likely to damage
116 non-JPEG files.* It is for this reason that JpegWasher will warn you if
117 you attempt to open and wash a non-JPEG file with it.
118
119 Output Files
120 ------------
121
122 JpegWasher never modifies an existing image file. Instead, it creates a
123 new file of the same type but with “_washed” appended to its name. For
124 example, processing ``foo.jpg`` will create ``foo_washed.jpg``. By
125 default, the new file will be created in the same directory as the file
126 being washed.
127
128 JpegWasher is Configurable
129 --------------------------
130
131 Both the whitelist and the destination directory for the washed files
132 are user-configurable in the Preferences menu.
133
134 Configuring the Whitelist
135 ~~~~~~~~~~~~~~~~~~~~~~~~~
136
137 There are two kinds of whitelist entries: those that match an entire
138 metadata key, and those that match a key prefix. The latter end in an
139 asterisk. The whitelist is case-sensitive; i.e. the entry
140 ``exif.image.colormap`` *will not* match the ``Exif.Image.ColorMap``
141 key.
142
143 That’s about It
144 ---------------
145
146 JpegWasher does not, and probably never will, do anything but remove
147 extraneous metadata from JPEG files.
148
149 First, I have no desire to re-invent the wheel. There are already
150 excellent open-source tools like Gimp for image editing, and ExifTool
151 and Exiv2 for general-purpose metadata editing (in fact, JpegWasher is
152 built on top of Exiv2). If you need the functionality of some other
153 tool, download and use it!
154
155 Second (and more importantly), I want JpegWasher to be simple, and
156 therefore easy to learn and easy to use. The more challenging an
157 information-security tool is to use, the less likely it is to be used
158 frequently, and the more likely it is that compromising information gets
159 disclosed.