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gnuplot demo script: image.dem

autogenerated by webify.pl on Tue Jan 20 11:43:42 2015
gnuplot version gnuplot 5.0 patchlevel 0
# demo for plotting images using pixels and binary 2d data
#
# This demo can be used for terminals supporting image display.
# Currently supported are:  X11, Aqua, postscript, png, pdf, svg,
# (e)pslatex, pstex, emf, wxt.

# Prepared by Dan Sebald
# History:
#	- Nov   2006 EAM: split into two files
#	- 9.23. 2003 ds: redone in response to discussion list feedback
#	- 5. 3. 2003 ds: 1st version

print ""
print "The plotting styles \`image\` and \`rgbimage\` are intended for plotting"
print "images described in a data file either in the convential ASCII format or"
print "in a binary format described by the qualifiers \`binary\` and \`using\`."
print "All pixels have an (x,y) or (x,y,z) coordinate.  These values can be"
print "included in the data file or implicitly determined with the sampling"
print "\'array\' key word and sampling periods \'dx\' and \'dy\'.  The key words"
print "\'rotate\' and, for 3d plots, \'perpendicular\' control orientation."
print "\nThe data for this image was stored as RGB triples, one byte per channel,"
print "without (x,y) coordinate information.  This yields a most compact file."
print "The plotting command is displayed on the graph."
print ""
set title "Larry Ewing's GIMP penguin on vacation basking in\nthe balmy waters off the coast of Murmansk"
set xrange [-10:137]
set yrange [-10:157]
set label "\"I flew here... by plane.  Why?  For the halibut.\"" at 64,135 center
plot 'blutux.rgb' binary array=(128,128) flipy format='%uchar' with rgbimage

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print ""
print "Images are typically stored in a file with the first datum being the"
print "top, left pixel.  Without the ability to translate coordinates, the"
print "the result would be an upside down image."
print ""
print "The key word \'array\' means an implied sample array is applied"
print "to generate the locations of file data using the sampling periods"
print "dx, dy and dz.  The x-dimension is always the contiguous points in"
print "a binary file.  The y-dimension is the line number which is incremented"
print "upon the x-dimension reaching the line length.  The z-dimension is"
print "the plane number which is incremented upon the y-dimension reaching"
print "the number of lines per plane."
print ""
print "To alter the location of the binary data when displayed via the \'plot\'"
print "command, use the key word \'rotate\' along with changing the sign of dx, dy"
print "and dz."
print ""
set title "Translations of position variables via 'using'"
set xrange [-10:275]
set yrange [-10:300]
unset key
set label "\"Time for a dip...\"" at 132,285 center
plot 'blutux.rgb' binary array=(128,128) flipy center=( 64,201 ) format='%uchar' with rgbimage, \
     'blutux.rgb' binary array=(128,128) flipy rotation=-90d center=(201,201) format='%uchar' with rgbimage, \
     'blutux.rgb' binary array=(128,128) flip=y rotate=3.1415 center=(201,64) format='%uchar' with rgbimage, \
     'blutux.rgb' binary array=(128,128) flip=y rot=0.5pi center=(64,64) format='%uchar' using 1:2:3 with rgbimage

Click here for minimal script to generate this plot




print ""
print "There is the ability to plot both color images and palette based"
print "images.  This is controlled by the styles \`image\`, which derives"
print "color information from the current palette, and \`rgbimage\`,"
print "which requires three components representing the red, blue and"
print "green primary color scheme."
print ""
print "By the way, if you have a mouse active, click the right button"
print "inside the image to isolate a portion of the image and see what"
print "happens."
print ""
unset key
set xrange [-10:137]
set yrange [-10:157]
set label 1 "\"I am the penguin, GOO GOO GOO JOOB.\"" at 63,140 center
set title "Palette mode 'image' used to produce psychedelic bird"
unset colorbox
plot 'blutux.rgb' binary array=(128,128) flipy format='%uchar%uchar%uchar' using ($1+$2+$3) with image

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print ""
print "Naturally, as with 3d color surfaces, the palette may be changed."
print "This is an example of gray scale."
print ""
print "Also, notice in the plot command the key word \'flipy\'.  This"
print "means to change the direction of the sample along the y dimension"
print "and is useful for the situation where images or other data are"
print "stored in some direction other than that of the Cartesion system."
print "Alone, \'flipD\' means do flipping in the D (x y or z) direction"
print "for all records.  Individual records can be controlled using the"
print "syntax \'flipD=#,...,#\', where # is \'0\' or \'1\'."
print ""
unset key
set xrange [-10:137]
set yrange [-10:157]
set tics out
set label 1 "\"This picture was taken by my friend Ansel Adams.\"" at 63,140 center
set title "The palette can be changed from color to gray scale"
set palette gray
unset colorbox
plot 'blutux.rgb' binary array=(128,128) flipy format='%uchar%uchar%uchar' using ($1+$2+$3)/3 with image

Click here for minimal script to generate this plot



unset label 1

print ""
print "Also, similar to 3d color surface plots, a color box showing the"
print "palette mapping scheme can be added to the plot.  The default"
print "location is the right edge of the plot.  The location can be set"
print "manually using \`set colorbox\` and \`set margin\`."
print ""
print "As a prelude to the next graph, resize the plot window to judge"
print "the refresh speed of the image drawing routine.  Notice that when"
print "the window is smaller, the image refresh is faster.  There is more"
print "decimation in the data of the original image and less data to plot."
print "Furthermore, the window continues to refresh at a reasonable rate"
print "even when the input image size becomes large (e.g., 1024 x 1024)"
print "because the number of pixels on the screen remains about the same"
print "while much of the hi resolution data is decimated."
print ""
unset key
set pm3d map
set xrange [10:117]
set yrange [10:117]
set tics out
set colorbox
set cbrange [0:255]
set title "As with 3d color surfaces, a color box may be added to the plot"
splot 'blutux.rgb' binary array=(128,128) flipy format='%uchar%uchar%uchar' using ($1+$2+$3)/3 with image

Click here for minimal script to generate this plot




print ""
print "The \'rotation\' key word works not only with angles of integer"
print "multiples of 90 degrees but also arbitrary rotations.  When"
print "constructing an image, Gnuplot verifies that pixel locations"
print "form a valid grid.  Pixel widths are based upon the grid"
print "spacing.  If the image orientation is aligned with the view"
print "axes, Gnuplot uses an efficient image driver routine.  Otherwise,"
print "individual pixels are drawn using polygon shapes."
print ""
print "Resize this window and compare the plot's refresh rate to that of"
print "the previous and next plot.  Notice how in this example if the"
print "window is small the image refresh does not speed up.  Unlike the"
print "image routine where image data is decimated, all color rectangles"
print "must be redrawn no matter the size of the output image."
print ""
print "Also notice how the center of the image matches the tuple specified"
print "with the key word \'center\' in the plot command.  Before doing the"
print "rotation, the image's natural center is subtracted, and after doing"
print "the rotation, the specified center is added."
print ""
set key
set xrange [-10:138]
set yrange [-10:138]
set tics out
set title "Polygons used to draw pixels for rotated images\nNotice the slower refresh rate than for the next plot"
unset colorbox
plot 'blutux.rgb' binary array=(128,128) dx=0.70711 dy=0.70711 flipy rotation=45d center=(63.5,63.5) format='%uchar' using ($1+$2+$3)/3 with image

Click here for minimal script to generate this plot




print ""
print "The image of this plot is rotated 90 degrees and can utilize the"
print "efficient image functions of terminal drivers.  The plot refresh"
print "is faster than the previous plot."
print ""
print "Furthermore, the image location in this case is specified via the"
print "\'origin\' key word.  As such, the rotation is done about the origin"
print "as opposed to the center of the image.  Notice the difference in"
print "axis ranges."
print ""
unset key
set xrange [-138:10]
set yrange [-10:138]
set tics out
set title "Terminal image routine used to draw plot rotated about origin\nNotice the faster refresh rate than for the previous plot"
unset colorbox
plot 'blutux.rgb' binary array=(128,128) dx=1 flip=y rotation=0.5pi origin=(0,0) format='%uchar' using ($1+$2+$3)/3 with image

Click here for minimal script to generate this plot




print ""
print "Algebraic manipulation of the input variables can select various"
print "components of the image.  Here are three examples where two"
print "channels--or analogous to the ASCII file, data \"columns\"--are ignored"
print "This is done by using \`*\` in the format to indicate that a variable"
print "of a certain size should be discarded.  For example, to select the"
print "green channel, \`%*uchar%uchar%*uchar\` is one alternative."
print ""
set size 1.0, 1.0
set origin 0.0, 0.0
set multiplot
set size 0.5,0.48
set origin 0.0,0.47
unset key
set xrange [-0.5:127.5]
set yrange [-0.5:127.5]
set tics out
set label 1 "Selection of the input channels via \`using\`" at 140,160 center
set title '"I do impersonations..."' offset 0,-0.5
plot 'blutux.rgb' binary array=(128,128) flip=y format='%uchar' using 1:2:3 with rgbimage
unset label 1
set size 0.5,0.48
set origin 0.5,0.47
set title '"A cardinal."'
plot 'blutux.rgb' binary array=(128,128) flip=y format='%uchar%*uchar%*uchar' using 1:(0):(0) with rgbimage
set size 0.5,0.48
set origin 0.0,0.0
set title '"A parrot."'
plot 'blutux.rgb' binary array=(128,128) flipy format='%*uchar%uchar%*uchar' using (0):1:(0) with rgbimage
set size 0.5,0.48
set origin 0.5,0.0
set title '"A bluebird."'
plot 'blutux.rgb' binary array=(128,128) flipy format='%*uchar%*uchar%uchar' using (0):(0):1 with rgbimage
unset multiplot

Click here for minimal script to generate this plot




print ""
print "The range of valid pixel values can be set via \`cbrange\`.  If the"
print "\`cbrange\` is in autoscale mode, gnuplot will set the color scale"
print "range of RGB images to [0:255] (8 bits of color info per channel)."
print "This is the case in the upper left image.  However, the image can be"
print "saturated by choosing a smaller range, as done in the upper right image."
print "Expanding the colorbox range will darken the image as in the bottom examples."
print ""
set size 1.0, 1.0
set origin 0.0, 0.0
set multiplot
set size 0.5,0.48
set origin 0.0,0.47
unset key
set xrange [-0.5:127.5]
set yrange [-0.5:127.5]
set tics out
set label 1 "Luminance adjustment via \`cbrange\`" at 140,160 center
set title 'Lake Mendota, "or Wonk-sheck-ho-mik-la!"' offset 0,-0.5
set cbrange [*:*]
plot 'blutux.rgb' binary array=(128,128) flipy format='%uchar' using 1:2:3 with rgbimage
unset label 1
set size 0.5,0.48
set origin 0.5,0.47
set title '"Lucky I brought sunscreen."'
set cbrange [0:200]
plot 'blutux.rgb' binary array=(128,128) flip=y format='%uchar' using 1:2:3 with rgbimage
set size 0.5,0.48
set origin 0.0,0.0
set title 'Sunset on the Terrace'
set cbrange [0:400]
plot 'blutux.rgb' binary array=(128,128) flip=y format='%uchar' using (1.5*$1):2:3 with rgbimage
set size 0.5,0.48
set origin 0.5,0.0
set title 'Sultry evening'
set cbrange [0:400]
plot 'blutux.rgb' binary array=(128,128) flipy format='%uchar' using 1:2:3 with rgbimage, '-' w points pt 7 ps 6 lt -2, '-' w points pt 7 ps 0.65 lt -2
110 100
e
10 95
38 120
82 102
26 82
93 108
41 99
123 84
e
unset multiplot

Click here for minimal script to generate this plot