identify Command in Linux
The identify command in Linux displays the format or characteristics of one or more images. It is a part of the ImageMagick suite of tools. Apart from displaying information in image format, it also reports whether an image is corrupt.
The information the identify command returns is image number, name, height, width, image format, number of bytes, number of colors, and number of seconds the command takes to read the image.
Table of Contents
Here is a comprehensive guide to the options available with the identify command −
- Prerequisites to Use identify Command
- Syntax of identify Command
- Options of identify Command
- Examples of identify Command in Linux
Prerequisites to Use identify Command
By default, the identify command may not be available in Linux. For verification, use the following command −
identify -version
If the above command shows a version, the identify command is installed. If it does not show the version then install it using the instructions mentioned below.
The identify tool is a part of the imagemagick suite. The imagemagic is a powerful open-source package that offers various tools to create, manipulate and convert images.
To install the imagemagick on Ubuntu, Kali Linux, Raspberry Pi OS, Debian, and Debian-based distributions, use the command given below −
sudo apt install imagemagick
To install it on Arch Linux, use −
sudo pacman -S imagemagick6
Syntax of identify Command
The syntax of the Linux identify command is as follows −
identify [options] [file]
The [options] field is used to use various options to identify command offers. The [file] field is used to specify the input image file.
Note − The identify command is entirely read-only. Some options may appear to modify the image. But the identify command does not change the image, it makes changes in the memory and shows the output. For example, the -crop option cuts the image in memory and reports the details of the modified image without affecting the original file.
Options of identify Command
The options for the identify command are listed below −
| Options | Description |
|---|---|
| -alpha | To control the alpha channel: on, off, set, opaque, transparent, extract, backgroun, or shape |
| -antialias | To remove pixel aliasing (smooth jagged edges) |
| -authenticate password | To use the password to decrypt the image |
| -channel type | To apply an option to specific image channels (like red, green, blue, and alpha) |
| -clip | To clip the image along the first path found in the 8BIM profile |
| -clip-mask filename | To associate a clip mask (stored in a separate file) with the image |
| -clip-path id | To clip the image along a named path from the 8BIM profile |
| -colorspace type | To change the image's colorspace (e.g., RGB, CMYK) |
| -crop geometry | To crop the image to a rectangular region as defined by the geometry |
| -define format:option | To set one or more image format-specific options |
| -density geometry | To define the horizontal and vertical density (resolution) of the image |
| -depth value | To set the bit depth of the image |
| -endian type | To specify the byte order (endianness) of the image: MSB (most significant byte) or LSB (least significant byte) |
| -extract geometry | To extract an area from the image based on geometry |
| -features distance | To analyze image features like contrast, correlation, and more |
| -format "string" | To output formatted image characteristics |
| -fuzz distance | To define the color distance where colors are considered equal |
| -gamma value | To apply gamma correction to adjust the brightness of the image |
| -interlace type | To choose the interlacing scheme for the image (e.g., none, JPEG, PNG) |
| -interpolate method | To define the pixel color interpolation method (e.g., NearestNeighbor, Bilinear, Bicubic) |
| -limit type value | To set resource limits (e.g., memory, map, time, etc.) for processing the image |
| -list type | To list supported types like Color, Configure, Delegate, Format, Magic, Module, Resource, or Type |
| -mask filename | To associate a mask (stored in a file) with the image |
| -matte | To store the matte (transparency) channel if present in the image |
| -moments | To report statistical moments of the image (e.g., mean, variance) |
| -monitor | To show progress during processing. |
| -ping | To efficiently determine image attributes without fully loading the image |
| -precision value | To set the maximum number of significant digits for printing image attributes |
| -quiet | To suppress all warning messages during image processing |
| -regard-warnings | To pay attention to warning messages (opposite of -quiet) |
| -respect-parentheses | To ensure that settings remain in effect until the boundary of parentheses is reached |
| -sampling-factor geometry | To define the horizontal and vertical sampling factors (for JPEG images) |
| -seed value | To set the seed for generating pseudo-random numbers (used for dithering, etc.) |
| -set attribute value | To set an image attribute (like image name, date, format) |
| -size geometry | To define the width and height of the image |
| -strip | To remove all profiles and comments from the image |
| -unique | To display the number of unique colors in the image |
| -units type | To set the units for image resolution (e.g., PixelsPerInch, PixelsPerCentimeter) |
| -verbose | To print detailed information about the image and processing steps |
| -virtual-pixel method | To define how to access pixels outside the image boundary (e.g., Background, Transparent, Tile) |
| -debug events | To display detailed debugging information |
| -help | To display program options |
| -list type | To display a list of supported option arguments |
| -log format | To define the format of debugging information |
| -version | To display the version of the program |
Examples of identify Command in Linux
This section demonstrates the usage of the Linux identify command with examples −
Displaying Information of a File
To display the information of an image file, use the identify command with the image file name −
identify image.jpg
The output shows the following attributes −
- Format (JPEG)
- Dimensions (2922x1862)
- Size/Offset (2922x1862 / +0+0)
- Color Depth (8-bit)
- Color Space (sRGB)
- Size (193746B)
- CPU Time (0.000u)
- Time Taken to Execute the Command (0:00.00)
Similarly, to display information of a bitmap image, use −
identify image.bmp
Displaying Verbose Information of a File
To display the detailed information of a file, use the -verbose option −
identify -verbose image.jpg
Displaying Progress while Loading Image
To display the progress of a loading image, use the -monitor option −
identify -monitor image.jpg
Displaying All the Supported Formats
To display all the supported formats, use the -list option with the format argument −
identify -list format
Displaying Information about all the Images in a Directory
To display information about all the images of the same extension, a wildcard can be used −
identify *.png
Displaying Information about a Cropped Image
To display the information of a cropped image, use the -crop option with the geometry specifying the crop section. For example, to split the image into 1920x1080 sections, use the identify command in the following way −
identify -crop 1920x1080 image.jpg
Displaying Help
To display the help about the identify command, use the -help option −
identify -help
Conclusion
The identify command in Linux is used to display the information of an image. It is a part of the ImageMagick suite.
To use the identify command on Linux, the imagemagick package must be installed. It is a handy tool to extract information about one or more images.