There are copious amounts of extra data associated with images (metadata), beyond the actual image pixels. This metadata can be useful, either for display, or for various calculations, or in modifying the behavior of later image processing operations. You can utilize percent escapes in a number of options, for example in -format or in montage -label, to print various properties and other settings associated with an image.
|Profile Data||Such as EXIF: data, containing focal lengths, exposures, dates, and in some cases GPS locations.|
|Attributes||These are directly involved with image data, and more commonly modified as part of normal image processing. These include width, height, depth, image type (colorspace), timing delays, and background color. Most specific percent escapes is to access this information.|
|Properties||These are stored as a table of free form strings, and are (if possible) saved with the image (especially in MIFF and PNG image file formats). These include: Labels, Captions, Comments.|
|Artifacts||These are various operational (expert) settings that are saved for use by various operators, or by the user for future use. It is just a table of free-form strings. They are not saved with the image when written. See Artifacts and Options below for details.|
|Options||Also operational (expert) settings that are saved for use by various operators, but are set globally for use by a whole image list (also not saved). See Artifacts and Options below.|
Percent Escape Handling
If you request a percent escape such as %[key] the setting is looked for in the following order until the first match has been found...
- Handle special prefixes such as 'artifact:' 'option:' 'exif:', or 'fx:'. This includes and calculations and or globs of those prefixes such as 'exif:*' or 'artifact:*' (see below).
- If key contains a glob pattern (but no known prefix) search free-form properties table.
- If key is a special image 'attribute' name (see list above) return the associated or calculated image attribute.
- Search for setting as a free-form 'property'
- Search for setting as a free-form 'artifact'
- Search for setting as a free-form 'option'
- Replace escape with empty string, and perhaps produce a warning.
Remember, all long name forms of percent escapes are handled in a is case insensitive manner.
You can now access the Artifact and Option free-form string tables directly, allowing you to override the above sequence, and avoid accessing an attribute or property of the same name.
Escape handling requires access to an image container. If none are available, a blank image is created to ensure the expression can be processed and a value returned. For example, magick -print "%[fx:.8765/3.14]" null: null:.
Single Letter Attribute Percent Escapes
Here are common single letter escapes (short form) is used to report the most common attributes and properties of an image, such as: the image filename filename, type, width, height.
|\||backslash, the next character is literal and not subject to interpretation|
|%%||a percent sign|
|%b||file size of image read in (use -precision 16 to force results in B)|
|%c||comment meta-data property|
|%d||directory component of path|
|%e||filename extension or suffix|
|%f||filename (including suffix)|
|%g||layer canvas page geometry (equivalent to "%Wx%H%X%Y")|
|%h||current image height in pixels|
|%i||image filename (note: becomes output filename for "info:")|
|%k||CALCULATED: number of unique colors|
|%l||label meta-data property|
|%m||image file format (file magic)|
|%n||number of images in current image sequence, report once per frame|
|%o||output filename (used for delegates)|
|%p||index of image in current image list|
|%q||quantum depth (compile-time constant)|
|%r||image class and colorspace|
|%s||scene number (from input unless re-assigned)|
|%t||filename without directory or extension (suffix)|
|%u||unique temporary filename (used for delegates)|
|%w||current width in pixels|
|%x||x resolution (density)|
|%y||y resolution (density)|
|%z||image depth (as read in unless modified, image save depth)|
|%A||image transparency channel. Values include Undefined (no transparency channel), Blend, Copy, or Update.|
|%B||file size of image read in bytes|
|%C||image compression type|
|%D||image GIF dispose method|
|%G||original image size (%wx%h; before any resizes)|
|%H||page (canvas) height|
|%M||Magick filename (original file exactly as given, including read mods)|
|%N||number of images in current image sequence, report once per image sequence|
|%O||page (canvas) offset ( = %X%Y )|
|%P||page (canvas) size ( = %Wx%H )|
|%Q||image compression quality ( 0 = default )|
|%S||?? scenes ??|
|%T||image time delay (in centi-seconds)|
|%U||image resolution units|
|%W||page (canvas) width|
|%X||page (canvas) x offset (including sign)|
|%Y||page (canvas) y offset (including sign)|
|%Z||unique filename (used for delegates)|
|%@||CALCULATED: trim bounding box (without actually trimming)|
|%#||CALCULATED: 'signature' hash of image values|
Here is a sample command and its output for an image with filename bird.miff and whose width is 512 and height is 480.
-> identify -format "%m:%f %wx%h" bird.miff MIFF:bird.miff 512x480
Note that all single letter percent escapes can also be used using long form (from IM version 6.7.6-9, see next). For example %[f] is equivalent to the %f short form.
WARNING: short form percent escapes are NOT performed when the percent is after a number. For example, 10%x10 does not expand the %x as a percent escape. If you specifically want to expand the 'x', use the long form which overrides this special case. EG: 10%[x]10.
Also be warned that calculated attributes can take some time to generate, especially for large images.
Long Form Attribute Percent Escapes
In addition to the above specific and calculated attributes are recognized when enclosed in braces (long form):
|%[basename]||base filename, no suffixes (as %t)|
|%[bit-depth]||Actual bit-depth of the pixel data|
|%[bounding-box]||upper left and lower right corners of the image bounding box|
|%[caption]||caption meta-data property|
|%[caption:lines]||returns the number lines generated when wrapping the caption|
|%[caption:pointsize]||returns the pointsize computed during caption: processing|
|%[channels]||??? channels in use - colorspace ???|
|%[colors]||Number of unique colors in the image (as of IM 126.96.36.199)|
|%[colorspace]||colorspace of Image Data (excluding transparency)|
|%[compression]||image compression type|
|%[convex-hull]||points that form a convex hull around the foreground object. Use -define convex-hull:background-color=color to identify the image background color. Use -fuzz to allow for a non-uniform background color.|
|%[convex-hull:extreme-points]||return the top, right, bottom, and left extreme points of the convex hull.|
|%[copyright]||ImageMagick Copyright String|
|%[depth]||depth of image for write (as input unless changed)|
|%[deskew:angle]||The deskew angle in degrees of rotation|
|%[directory]||directory part of filename (as %d)|
|%[distortion]||how well an image resembles a reference image (-compare)|
|%[dominant-color]||return the dominate image color in hex. Preceed usage with -kmeans.|
|%[entropy]||CALCULATED: entropy of the image|
|%[extension]||extension part of filename (as %e)|
|%[gamma]||value of image gamma|
|%[group]||??? window group ???|
|%[height]||original height of image (when it was read in)|
|%[histogram:contrast-stretch]||computed min and max contrast stretch percentage|
|%[histogram:linear-stretch]||computed min and max linear stretch percentage|
|%[interlace]||Image interlace mode (as of IM 188.8.131.52)|
|%[kurtosis]||CALCULATED: kurtosis statistic of image|
|%[label]||label meta-data property|
|%[label:pointsize]||returns the pointsize computed during label: processing|
|%[magick]||coder used to read image (not the file suffix)|
|%[max]||CALCULATED: maximum value statistic of image|
|%[mean]||CALCULATED: average value statistic of image|
|%[median]||CALCULATED: median value statistic of image|
|%[min]||CALCULATED: minimum value statistic of image|
|%[minimum-bounding-box]||Use -define convex-hull:background-color=color to identify the image background color. Use -fuzz to allow for a non-uniform background color. In addition to the bounding box points, these properties are set: minimum-bounding-box:area, minimum-bounding-box:width, minimum-bounding-box:height, minimum-bounding-box:angle, and minimum-bounding-box:unrotate.|
|%[opaque]||CALCULATED: is image fully-opaque?|
|%[page]||Virtual canvas (page) geometry|
|%[papersize:name]||paper size for name in pixels at 72DPI (e.g. papersize:A4)|
|%[profile:icc]||ICC profile info|
|%[profile:icm]||ICM profile info|
|%[profiles]||list of any embedded profiles|
|%[quality]||Image quality value (as of IM 184.108.40.206)|
|%[rendering-intent]||Image rendering intent (as of IM 220.127.116.11)|
|%[resolution.x]||X density (resolution) without units|
|%[resolution.y]||Y density (resolution) without units|
|%[scene]||original scene number of image in input file|
|%[size]||original size of image (when it was read in)|
|%[skewness]||CALCULATED: skewness statistic of image|
|%[standard-deviation]||CALCULATED: standard deviation statistic of image|
|%[type]||CALCULATED: image type|
|%[unique]||unique temporary filename ???|
|%[units]||image resolution units|
|%[version]||Version Information of this running ImageMagick|
|%[width]||original width of image (when it was read in)|
|%[zero]||zero (unique filename for delegate use)|
All other long forms of percent escapes (not single letter long form) are handled in a case insensitive manner. Such escapes will attempt to look up that name specific data sources.
The primary search space (if not a specific attribute listed above) is a free-form property string. Such strings are associated and saved with images, and are typically set using either the -set CLI option (or API equivalent), or from special convenience options (such as -label, -comment, -caption).
These convenience options are globally saved (as 'global options' so thay can be set before images are read), and later are transferred to the property of individual images, only when they are read in. At that time any internal percent escape present is then handled.
To change a property of an image already in memory, you need to use -set.
Note that properties, like attributes (and profiles), are saved with images when write, if the image file format allows.
Artifacts and Options
The previous percent escapes are associated with the primary Attributes and Properties. Which is the original and primary focus of such percent escapes.
However there are many operational settings that are used by various ImageMagick operators that can be useful to set and later access. These consist of per-image Artifacts, and Global options (associated with a list of images, typically the current image list).
Note that the major difference between an artifact and a property is that artifacts, being an internal operational setting, is not saved with images (if such is possible).
For example when you use -define 'distort:viewport=100x100' you are in fact generating a global option, which the -distort operator will use to modify its behavior (distorted output image 'view').
An Option is essentially an Artifact that has been stored globally as part of a list of images (specifically a 'Wand' of images). As such they are identical, in that a Option, is simply a global Artifact for all the associated images.
As such you can use -set 'option:distort:viewport' '100x100' to achieve the same result of setting a Artifact for the disort operation to use.
Internal Handling of a Global Option...
The Core library ('MagickCore') does not generally directly understand Global Options. As such, continuing the previous example, the DistortImages() function only looks up an artifact to discover if a 'viewport' has been provided to it.
How Global Options are used when a library function requests an Artifact is one of the key differences between IMv6 and IMv7.
Sets a link back to the global options data, so that if a specific per-image Artifact is not found , then it will look for a equivalent global Option for that image list. directly. This saves coping these free-form options into artifacts repeatedly, and means you can now separately define a global option for a list, and a individual overriding artifact for a specific image in that list.
Note that many API's that do not use Wands (PerlMagick for example using arrays of images rather than a Wand). In these API's you will not have Global Options, only per-image Artifacts.
In summery a Global Option, if available, is equivalent to a per-image Artifact.
Glob-Pattern Listing of Properties, Artifacts and Options
The setting can contain a glob pattern. As such you can now list all free-form string properties, artifacts, and options, (but not specific image attributes) using...
magick ... \ -print "__Properties__\n%[*]" \ -print "__Artifacts__\n%[artifact:*]" \ -print "__Options__\n%[option:*]" \ ...
The format of glob patterns are very specific and as such is generally only used to list specific settings, such as when debugging, rather than being used for image processing use.
Calculated Percent Escape Prefixes
There are some special prefixes (before the first ':') which performs calculations based on the user provided string that follows that prefix. For example you can do a numerical calculation use %[fx:...] to evaluate the given FX expressions:
Use pixel: or hex: to evaluate a pixel color as defined by the FX expression:
Use -define to specify the color compliance (e.g. -define pixel:compliance=css).
Specific Profile Percent Escape Prefixes
You can also use the following special formatting syntax to print EXIF mage meta-data that was included in the image read in:
Choose tag from the following:
* (print all EXIF tags, in keyword=data format) ! (print all EXIF tags, in tag_number data format) #hhhh (print data for EXIF tag #hhhh) ImageWidth ImageLength BitsPerSample Compression PhotometricInterpretation FillOrder DocumentName ImageDescription Make Model StripOffsets Orientation SamplesPerPixel RowsPerStrip StripByteCounts XResolution YResolution PlanarConfiguration ResolutionUnit TransferFunction Software DateTime Artist WhitePoint PrimaryChromaticities TransferRange JPEGProc JPEGInterchangeFormat JPEGInterchangeFormatLength YCbCrCoefficients YCbCrSubSampling YCbCrPositioning ReferenceBlackWhite CFARepeatPatternDim CFAPattern BatteryLevel Copyright ExposureTime FNumber IPTC/NAA EXIFOffset InterColorProfile ExposureProgram SpectralSensitivity GPSInfo ISOSpeedRatings OECF EXIFVersion DateTimeOriginal DateTimeDigitized ComponentsConfiguration CompressedBitsPerPixel ShutterSpeedValue ApertureValue BrightnessValue ExposureBiasValue MaxApertureValue SubjectDistance MeteringMode LightSource Flash FocalLength MakerNote UserComment SubSecTime SubSecTimeOriginal SubSecTimeDigitized FlashPixVersion ColorSpace EXIFImageWidth EXIFImageLength InteroperabilityOffset FlashEnergy SpatialFrequencyResponse FocalPlaneXResolution FocalPlaneYResolution FocalPlaneResolutionUnit SubjectLocation ExposureIndex SensingMethod FileSource SceneType
Surround the format specification with quotation marks to prevent your shell from misinterpreting any spaces and square brackets.
The following special formatting syntax can be used to print IPTC information contained in the file:
Select dataset and record from the following:
Envelope Record 1:00 Model Version 1:05 Destination 1:20 File Format 1:22 File Format Version 1:30 Service Identifier 1:40 Envelope Number 1:50 Product ID 1:60 Envelope Priority 1:70 Date Sent 1:80 Time Sent 1:90 Coded Character Set 1:100 UNO (Unique Name of Object) 1:120 ARM Identifier 1:122 ARM Version Application Record 2:00 Record Version 2:03 Object Type Reference 2:05 Object Name (Title) 2:07 Edit Status 2:08 Editorial Update 2:10 Urgency 2:12 Subject Reference 2:15 Category 2:20 Supplemental Category 2:22 Fixture Identifier 2:25 Keywords 2:26 Content Location Code 2:27 Content Location Name 2:30 Release Date 2:35 Release Time 2:37 Expiration Date 2:38 Expiration Time 2:40 Special Instructions 2:42 Action Advised 2:45 Reference Service 2:47 Reference Date 2:50 Reference Number 2:55 Date Created 2:60 Time Created 2:62 Digital Creation Date 2:63 Digital Creation Time 2:65 Originating Program 2:70 Program Version 2:75 Object Cycle 2:80 By-Line (Author) 2:85 By-Line Title (Author Position) [Not used in Photoshop 7] 2:90 City 2:92 Sub-Location 2:95 Province/State 2:100 Country/Primary Location Code 2:101 Country/Primary Location Name 2:103 Original Transmission Reference 2:105 Headline 2:110 Credit 2:115 Source 2:116 Copyright Notice 2:118 Contact 2:120 Caption/Abstract 2:122 Caption Writer/Editor 2:125 Rasterized Caption 2:130 Image Type 2:131 Image Orientation 2:135 Language Identifier 2:150 Audio Type 2:151 Audio Sampling Rate 2:152 Audio Sampling Resolution 2:153 Audio Duration 2:154 Audio Outcue 2:200 ObjectData Preview File Format 2:201 ObjectData Preview File Format Version 2:202 ObjectData Preview Data Pre-ObjectData Descriptor Record 7:10 Size Mode 7:20 Max Subfile Size 7:90 ObjectData Size Announced 7:95 Maximum ObjectData Size ObjectData Record 8:10 Subfile Post ObjectData Descriptor Record 9:10 Confirmed ObjectData Size