VIPS from the command-line
Using VIPS — How to use the VIPS library from the command-line
Use the vips command to execute VIPS operations from the command-line. For example:
$ vips rot k2.jpg x.jpg d90
Will rotate the image
k2.jpg by 90 degrees
anticlockwise and write the result to the file
If you don't give any arguments to an operation,
vips will give a short description, for example:
$ vips rot rotate an image usage: rot in out angle where: in - Input image, input VipsImage out - Output image, output VipsImage angle - Angle to rotate image, input VipsAngle default: d90 allowed: d0, d90, d180, d270
There's a straightforward relationship with the C API: compare this to
the API docs for
vips_rot(), for example.
Listing all operations
You can list all classes with:
$ vips -l ... VipsOperation (operation), operations VipsSystem (system), run an external command VipsArithmetic (arithmetic), arithmetic operations VipsBinary (binary), binary operations VipsAdd (add), add two images ... etc.
Each line shows the canonical name of the class (for example
VipsAdd), the class nickname
add in this case), and a short description.
Some subclasses of operation will show more: for example, subclasses of
VipsForeign will show some of the extra flags
supported by the file load/save operations.
The API docs have a handy table of all vips operations, if you want to find out how to do something, try searching that.
Many operations take optional arguments. You can supply these as command-line options, for example:
$ vips gamma gamma an image usage: gamma in out where: in - Input image, input VipsImage out - Output image, output VipsImage optional arguments: exponent - Gamma factor, input gdouble default: 2.4 min: 1e-06, max: 1000 operation flags: sequential-unbuffered
vips_gamma() applies a gamma factor to an image. By
default, it uses 2.4, the sRGB gamma factor, but you can specify any
gamma with the
Use it from the command-line like this:
$ vips gamma k2.jpg x.jpg --exponent 0.42
This will read file
k2.jpg, un-gamma it, and
write the result to file
Some operations take arrays of values as arguments, for example,
vips_affine() needs an array of four numbers for the
2x2 transform matrix. You pass arrays as space-separated lists, for
$ vips affine k2.jpg x.jpg "2 0 0 1"
You may need the quotes to stop your shell breaking the argument at
vips_bandjoin() needs an array of input images to
join, run it like this:
$ vips bandjoin "k2.jpg k4.jpg" x.tif
Implicit file format conversion
vips will automatically convert between image file formats for you. Input images are detected by sniffing their first few bytes; output formats are set from the filename suffix. You can see a list of all the supported file formats with something like:
$ vips -l foreign
Then get a list of the options a format supports with, for example:
$ vips jpegsave
You can pass options to the implicit load and save operations enclosed in square brackets after the filename. For example:
vips affine k2.jpg x.jpg[Q=90,strip] "2 0 0 1"
x.jpg at quality level 90 and will
strip all metadata from the image.
Because each operation runs in a separate process, you can't use libvips's chaining system to join operations together, you have to use intermediate files. The command-line interface is therefore quite a bit slower than Python or C.
The best alternative is to use vips files for intermediates. Something like:
vips invert input.jpg t1.v vips affine t1.v output.jpg "2 0 0 1" rm t1.v
Finally, vips has a couple of useful extra options.
--vips-progressto get vips to display a simple progress indicator.
--vips-leakand vips will leak-test on exit, and also display an estimate of peak memory use.
G_MESSAGES_DEBUG=VIPSand GLib will display informational and debug messages from libvips.
VIPS comes with a couple of other useful programs. vipsheader is a command which can print image header fields. vipsedit can change fields in vips format images. vipsthumbnail can make image thumbnails quickly.