convert(1)
convert(1)
convert - converts an input file using one image format to
an output file with a differing image format.
SYNOPSIS
convert [ options ... ] input file output file
DESCRIPTION
convert converts an input file using one image format to an
output file with a differing image format.
convert recognizes the following image formats:
Tag Description
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---------------------------------------------------------------------
ALPHA Raw alpha bytes.
AVS AVS X image file.
BMP Microsoft Windows bitmap image file.
CMYK Raw cyan, magenta, yellow, and black bytes.
EPS Adobe Encapsulated PostScript file.
FAX Group 3.
FITS Flexible Image Transport System.
GIF Compuserve Graphics image file.
GRAY Raw gray bytes.
HISTOGRAM
IRIS SGI RGB image file.
JPEG
MIFF Magick image file format.
MTV
PCD Photo CD.
PCX ZSoft IBM PC Paintbrush file.
PICT Apple Macintosh QuickDraw/PICT file.
PNM Portable bitmap.
PS Adobe PostScript file.
PS2 Adobe Level II PostScript file.
RGB Raw red, green, and blue bytes.
RLE Utah Run length encoded image file; read only.
SUN SUN Rasterfile.
TEXT raw text file; read only.
TGA Truevision Targa image file.
TIFF Tagged Image File Format.
VICAR read only.
VIFF Khoros Visualization image file.
X select image from X server screen.
XC constant image of X server color. Specify the desired
color as the filename.
XBM X11 bitmap file.
XPM X11 pixmap file.
XWD X Window System window dump image file.
YUV Raw Y, U, and V bytes. U and V, normally -0.5 through
0.5, are normalized to the range 0 through 255 to fit
within a byte.
EXAMPLES
To convert a MIFF image of a cockatoo to a SUN raster image,
use:
convert cockatoo.miff sun:cockatoo.ras
To convert a multi-page Postscript document to individual
FAX pages, use:
convert -monochrome document.ps fax:page
To convert a TIFF image to a Postscript A4 page with the
image in the lower left-hand corner, use:
convert -page 595x842+0+0 image.tiff document.ps
To convert a raw GRAY image to a portable graymap, use:
convert -geometry 768x512 gray:raw image.pnm
OPTIONS
-alpha
store alpha channel if the image has one.
-border xfP
surround the image with a border or color. See X(1)
for details about the geometry specification.
The color of the border is obtained from the X server
and is defined as bordercolor (class borderColor). See
X(1) for details.
-clip x{+-}{+-}
preferred size and location of the clipped image. See
X(1) for details about the geometry specification.
Use clipping to crop a particular area of an image.
-colors value
preferred number of colors in the image.
The actual number of colors in the image may be less
than your request, but never more. Note, this is a
color reduction option. Images with less unique colors
than specified with this option will remain unchanged.
Refer to quantize(9) for more details.
Note, options -dither, -colorspace, and -treedepth
affect the color reduction algorithm.
-colorspace value
the type of colorspace: GRAY, RGB, XYZ, YCbCr, YIQ, or
YUV.
Color reduction, by default, takes place in the RGB
color space. Empirical evidence suggests that
distances in color spaces such as YUV or YIQ correspond
to perceptual color differences more closely than do
distances in RGB space. These color spaces may give
better results when color reducing an image. Refer to
quantize(9) for more details.
The -colors or -monochrome option is required for this
option to take effect.
-compress type
the type of image compression: QEncoded or
RunlengthEncoded.
Specify +compress to store the binary image in an
uncompressed format. The default is the compression
type of the specified image file.
-density x
vertical and horizontal density of the image.
This option specifies an image density for a Postscript
page. The default is 72 dots per inch in the
horizontal and vertical direction. Use this option to
alter the default density.
-display host:display[.screen]
specifies the X server to contact; see X(1).
-dither
apply Floyd/Steinberg error diffusion to the image.
The basic strategy of dithering is to trade intensity
resolution for spatial resolution by averaging the
intensities of several neighboring pixels. Images
which suffer from severe contouring when reducing
colors can be improved with this option.
The -colors option is required for dithering to take
effect.
-enhance
apply a digital filter to enhance a noisy image.
-font name
This option specifies the font to be used for
displaying normal text. The default is fixed.
-gamma value
level of gamma correction.
The same color image displayed on two different
workstations may look different due to differences in
the display monitor. Use gamma correction to adjust
for this color difference. Reasonable values extend
from 0.8 to 2.3.
You can apply separate gamma values to the red, green,
and blue channels of the image with a gamma value list
delineated with commas (i.e. 1.7,2.3,1.2).
-geometry {%}x{%}{!}
the width and height of the image.
By default, the width and height are maximum values.
That is, the image is expanded or contracted to fit the
width and height value while maintaining the aspect
ratio of the image. Append an exclamation point to the
geometry to force the image size to exactly the size
you specify. For example, if you specify 640x480! the
image width is set to 640 pixels and height to 480. If
only one factor is specified, both the width and height
assume the value.
To specify a percentage width or height instead, append
%. The image size is multiplied by the width and
height percentages to obtain the final image
dimensions. To increase the size of an image, use a
value greater than 100 (e.g. 125%). To decrease an
image's size, use a percentage less than 100.
If the specified image size is smaller than the actual
image size, the image is first reduced to an integral
of the specified image size with an antialias digital
filter. The image is then scaled to the exact
specified image size with pixel replication. If the
specified image size is greater than the actual image
size, the image is first enlarged to an integral of the
specified image size with bilinear interpolation. The
image is then scaled to the exact specified image size
with pixel replication.
Use this option to specify the width and height of raw
images whose dimensions are unknown such as GRAY, RGB,
and CMYK.
-interlace type
the type of interlacing scheme: NONE, LINE, or PLANE.
This option is used to specify the type of interlacing
scheme for raw image formats such as RGB or YUV. NONE
means do not interlace (RGBRGBRGBRGBRGBRGB...), LINE
uses scanline interlacing
(RRR...GGG...BBB...RRR...GGG...BBB...), and PLANE uses
plane interlacing (RRRRRR...GGGGGG...BBBBBB...).
-inverse
apply color inversion to image.
The red, green, and blue intensities of an image are
negated.
-monochrome
transform the image to black and white.
-noise
reduce the noise in an image with a noise peak
elimination filter.
The principal function of noise peak elimination filter
is to smooth the objects within an image without losing
edge information and without creating undesired
structures. The central idea of the algorithm is to
replace a pixel with its next neighbor in value within
a 3 x 3 window, if this pixel has been found to be
noise. A pixel is defined as noise if and only if this
pixel is a maximum or minimum within the 3 x 3 window.
-normalize
transform image to span the full range of color values.
This is a contrast enhancement technique.
-page x{+-}{+-}
preferred size and location of the Postscript page.
Use this option to specify the dimensions of the
Postscript page in picas or a TEXT page in pixels. The
default for a Postscript page is to center the image on
a letter page 612 by 792 dots per inch. The left and
right margins are 18 picas and the top and bottom 94
picas (i.e. 612x792+18+94). Other common sizes are:
540x720 Note
612x1008 Legal
842x1190 A3
595x842 A4
421x595 A5
297x421 A6
709x1002 B4
612x936 U.S. Foolscap
612x936 European Foolscap
396x612 Half Letter
792x1224 11x17
1224x792 Ledger
The page geometry is relative to the vertical and
horizontal density of the Postscript page. See
-density for details.
The default page dimensions for a TEXT image is
612x792+36+36.
-quality value
JPEG quality setting.
Quality is 0 (worst) to 100 (best). The default is 85.
-reflect
create a "mirror image" by reflecting the image
scanlines.
-roll {+-}{+-}
roll an image vertically or horizontally. See X(1) for
details about the geometry specification.
A negative x offset rolls the image left-to-right. A
negative y offset rolls the image top-to-bottom.
-rotate degrees
apply Paeth image rotation to the image.
Empty triangles left over from rotating the image are
filled with the color defined by the pixel at location
(0,0). Refer to -border to choose a specific color.
-scene value
image scene number.
-shear x
shear the image along the X or Y axis by a positive or
negative shear angle.
Shearing slides one edge of an image along the X or Y
axis, creating a parallelogram. An X direction shear
slides an edge along the X axis, while a Y direction
shear slides an edge along the Y axis. The amount of
the shear is controlled by a shear angle. For X
direction shears, x degrees> is measured relative to
the Y axis, and similarly, for Y direction shears y
degrees is measured relative to the X axis.
Empty triangles left over from shearing the image are
filled with the color defined by the pixel at location
(0,0). Refer to -border to choose a specific color.
-treedepth value
Normally, this integer value is zero or one. A zero or
one tells convert to choose a optimal tree depth for
the color reduction algorithm.
An optimal depth generally allows the best
representation of the source image with the fastest
computational speed and the least amount of memory.
However, the default depth is inappropriate for some
images. To assure the best representation, try values
between 2 and 8 for this parameter. Refer to
quantize(9) for more details.
The -colors option is required for this option to take
effect.
-undercolor x
control undercolor removal and black generation on CMYK
images.
This option enables you to perform undercolor removal
and black generation on CMYK images-- images to be
printed on a four-color printing system. You can
control how much cyan, magenta, and yellow to remove
from your image and how much black to add to it. The
standard undercolor removal is 1.0x1.0. You'll
frequently get better results, though, if the
percentage of black you add to your image is slightly
higher than the percentage of C, M, and Y you remove
from it. For example you might try 0.5x0.7.
-verbose
print detailed information about the image.
This information is printed: image scene number; image
name; converted image name; image size; the image
class (DirectClass or PseudoClass); the total number
of unique colors; and the number of seconds to read
and convert the image.
Change '-' to '+' in any option above to reverse its effect.
For example, specify +alpha to store the image without its
alpha channel.
By default, the image format is determined by its magic
number. To specify a particular image format, precede the
filename with an image format name and a colon (i.e.
ps:image) or specify the image type as the filename suffix
(i.e. image.ps). See DESCRIPTION for a list of valid
formats.
When you specify X as your image type, the filename has
special meaning. It specifies an X window by id, name, or
root. If no filename is specified, the window is selected
by clicking the mouse in the desired window.
Specify input_file as - for standard input, output_file as -
for standard output. If input_file has the extension .Z or
.gz, the file is uncompressed with uncompress or gunzip
respectively. If output_file has the extension .Z or .gz,
the file size is compressed using with compress or gzip
respectively. Finally, precede the image file name with |
to pipe to or from a system command. If output_file already
exists, you will be prompted as to whether it should be
overwritten.
Single images are written with the filename you specify.
However, multi-part images (i.e. a multi-page Postscript
document) are written with the filename followed by a period
(.) and the scene number. You can change this behavior by
embedding a printf format specification in the file name.
For example,
image%02d.miff
would produce files image00.miff, image01.miff, etc.
ENVIRONMENT
display
To get the default host, display number, and screen.
SEE ALSO
display(1), animate(1), mogrify(1), quantize(9), X(1),
miff(5)
COPYRIGHT
Copyright 1994 E. I. du Pont de Nemours & Company
Permission to use, copy, modify, distribute, and sell this
software and its documentation for any purpose is hereby
granted without fee, provided that the above copyright
notice appear in all copies and that both that copyright
notice and this permission notice appear in supporting
documentation, and that the name of E. I. du Pont de Nemours
& Company not be used in advertising or publicity pertaining
to distribution of the software without specific, written
prior permission. E. I. du Pont de Nemours & Company makes
no representations about the suitability of this software
for any purpose. It is provided "as is" without express or
implied warranty.
E. I. du Pont de Nemours & Company disclaims all warranties
with regard to this software, including all implied
warranties of merchantability and fitness, in no event shall
E. I. du Pont de Nemours & Company be liable for any
special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits,
whether in an action of contract, negligence or other
tortuous action, arising out of or in connection with the
use or performance of this software.
AUTHORS
John Cristy, E.I. du Pont De Nemours & Company Incorporated
ImageMagick Last change: 10 October 1992