econvert - Online in the Cloud

PROGRAM:

NAME

econvert - image converter of the ExactImage toolkit

SYNOPSIS

econvert [option...] [{-i | --input} input-file...] [{-o | --output} output-file...]

econvert {-h | --help}

DESCRIPTION

ExactImage is a fast C++ image processing library. Unlike many other library frameworks it
allows operation in several color spaces and bit depths natively, resulting in low memory
and computational requirements.

econvert is a command line frontend for the image processing library and mimics
ImageMagick's convert. However econvert syntax is not compatible with convert.

OPTIONS

Input/output
-i file, --input file
Read image from the specified file. Optionally, filenames can be prefixed with format
name, e.g. jpg:- or raw:rgb8-dump.

-o file, --output file
Save output image to the specified file. Optionally, filenames can be prefixed with
format name, e.g. jpg:- or raw:rgb8-dump.

-a file, --append file
Append output image to the specified file. Existing image must have the same width as
the appended one. Optionally, filenames can be prefixed with format name, e.g. jpg:-
or raw:rgb8-dump.

--compress method
Use the specified compression method for writing images, e.g. G3, G4, Zip, ... The
default depends on the output format.

--decompress method
Use the specified decompression method for reading images.

--quality n
Use the specified quality used for writing compressed images. Valid values are
integers from 0 to 100. The default is 75.

--resolution xdpi [ydpi]
Set metadata resolution.

--size width height
Set image dimensions for raw images.

--split file...
Split the image in Y-direction into multiple images.

Scaling, cropping, transformations
--bicubic-scale x
Scale image data with bi-cubic filter. Use scale factor x.

--bilinear-scale x
Scale image data with bi-linear filter. Use scale factor x.

--box-scale x
(Down)scale image data with box filter. Use scale factor x.

--ddt-scale x
Scale image data with data dependent triangulation. Use scale factor x.

--nearest-scale x
Scale image data to nearest neighbour. Use scale factor x.

--scale x
Scale image data using a method suitable for specified factor x.

--thumbnail x
Quick and dirty down-scale for a thumbnail. Use scale factor x.

--crop x y w h
Crop the specified area out of the image.

--fast-auto-crop
Fast auto crop.

--flip
Flip the image vertically.

--flop
Flip the image horizontally.

--rotate n
Rotate the image n degrees.

Colors
--brightness x
Change the image brightness.

--contrast x
Change the image contrast.

--saturation x
Change the image saturation.

--lightness x
Change the image lightness.

--hue x
Change the image hue.

--negate
Negate the image.

--gamma x
Change the image gamma.

--normalize
Transform the image to span the full color range.

--colorspace colorspace
Convert image colorspace. Valid values are: BW, BILEVEL, GRAY, GRAY1, GRAY2, GRAY4,
RGB, YUV and CYMK.

--floyd-steinberg n
Perform Floyd-Steinberg dithering using n shades.

--riemersma n
Perform Riemersma dithering using n shades.

Filters
--blur stdev
Perform gaussian blur with standard deviation stdev.

--deinterlace
Shuffle every 2nd line.

--edge
Detect edges.

--convolve x11 x12 ... x1n ... xn1 xn2 ... xnn
Convolve the image using the specified convolution matrix.

Drawing
--foreground color
Set foreground color.

--background color
Set background color.

--font font
Use the specified font for drawing text.

--text-rotation n
Use the specified text rotation.

--text x1 y1 height text
Draw text.

--stroke-width n
Set stroke width for vector primitives.

--line x1 y1 x2 y2
Draw a line.

Help
-h, --help
Display help text and exit.

EXAMPLES

Basics
Image data must be read using -i or --input, processing routines are selected by their
name with two leading dashes (e.g. --rotate) and at any point the data might be written
into a file with -o or --output, for example:

econvert -i lenea.tiff --box-scale 0.5 -o medium.png --box-scale 0.5 -o little.png

Lossless transformations of JPEG files
The library delays image decoding as much as possible and provides lossless algorithms to
work on compressed data (such as JPEGs) directly:

econvert -i AV220-Scan.JPG --resolution 300x300 -o 1.jpg --rotate 90 -o 2.jpg --rotate 180 -o 3.jpg --rotate -90 -o 4.jpg --flip -o 5.jpg --flop -o 6.jpg --scale 0.25 -o thumb.jpg

In this example 1.jpg will be created from the original JPEG DCT coefficients, those
coefficients will be rearranged and 2.jpg, 3.jpg, 4.jpg, 5.jpg and 6.jpg will be written
without any additional loss in quality. Only at the end, for image thumb.jpg, the DCT will
actually be decoded — but due to the accelerated JPEG scaling only partially.

Thumbnails of bi-level images
When 1 bit, black and white, images are scaled down, the output often looks bad, as the
library algorithms always operate in the color-space the image data is stored in. To work
around this problem, the colorspace must be changed (e.g. to 8 bit gray) before applying
the box scaler. At the end the result might be converted back to just a few shades of gray
such as 2 or 4 bit:

econvert -i avision-bw-scan.pbm --colorspace gray8 --box-scale 0.125 --colorspace gray2 -o thumb.png

Faster JPEG down-scaling
If you don't care about quality, only about throughput, you can force nearest neighbor
scaling by just specifying a scale factor the JPEG decoder can accelerate (½, ¼, or 1/8)
and apply the remaining scaling manually. To achieve faster scaling with the effective
factor 1/3:

econvert -i big.jpg --scale .5 --nearest-scale 0.66 -o thumb.jpg

Working with digital camera RAW data
Wide range of digital camera RAW formats is supported. Usually decoding of RAW data should
be transparent and automatic, however some formats also are also valid TIFF files and the
embedded thumbnail might be picked by in favour of the actual RAW content. This this cases
the dcraw decoder can explicitly be requested with the decoder prefix of the input
parameter:

econvert -i dcraw:img_0123.cr2 ...

To quickly extract the embedded thumbnail preview, specify thumb as decompression method
before the image is loaded:

econvert --decompress thumb -i dcraw:img_0123.cr2 ...

Loading arbitrary raw data
It is possible to load arbitrary raw data via the raw: codec specification; color-depth
(colorspace) and size for the raw data have to be explicitly specified:

econvert --size 1696x32 --colorspace rgb8 -i raw:data-file ...

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