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<H1><A NAME="SECTION030120000000000000000"></A>
<A NAME="commands_set_style_image"></A><A NAME="set_style_image"></A><A NAME="plotting_styles_image"></A><A NAME="style_image"></A><A NAME="image"></A><A NAME="1769"></A>
<A NAME="rgbimage"></A><A NAME="1771"></A>
<A NAME="rgbalpha"></A><A NAME="1773"></A>
<BR>
Image
</H1>
The <B>image</B>, <B>rgbimage</B>, and <B>rgbalpha</B> plotting styles all project a
uniformly sampled grid of data values onto a plane in either a 2D or 3D.
The input data may be an actual bitmapped image, perhaps converted from a
standard format such as PNG, or a simple array of numerical values.
<P>
<A NAME="1777"></A>
This figure illustrates generation of a heat map from an array of scalar values.
The current palette is used to map each value onto the color assigned to the
corresponding pixel.
<BR>
<PRE>
plot '-' matrix with image
5 4 3 1 0
2 2 0 0 1
0 0 0 1 0
0 1 2 4 3
e
e
</PRE>
<BR>
<P>
Each pixel (data point) of the input 2D image will become a rectangle or
parallelipiped in the plot. The coordinates of each data point will determine
the center of the parallelipiped. That is, an M x N set of data will form an
image with M x N pixels. This is different from the pm3d plotting style, where
an M x N set of data will form a surface of (M-1) x (N-1) elements. The scan
directions for a binary image data grid can be further controlled by additional
keywords. See <B>binary general keywords flipx (p. <A HREF="node131.html#binary_general_keywords_flipx"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>)<A NAME="1781"></A></B>, <B>center (p. <A HREF="node133.html#center"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>)<A NAME="1783"></A></B>, and <B>rotate (p. <A HREF="node134.html#rotate"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>)<A NAME="1785"></A></B>.
<P>
Image data can be scaled to fill a particular rectangle within a 2D plot
coordinate system by specifying the x and y extent of each pixel.
See <B>binary general keywords dx (p. <A HREF="node130.html#binary_general_keywords_dx"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>)<A NAME="1787"></A></B> and <B>dy (p. <A HREF="node130.html#dy"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>)<A NAME="1789"></A></B>. To generate the figure at the right,
the same input image was placed multiple times, each with a specified dx, dy,
and origin. The input PNG image of a building is 50x128 pixels. The tall
building was drawn by mapping this using <B>dx=0.5 dy=1.5</B>. The short building
used a mapping <B>dx=0.5 dy=0.35</B>.
<P>
The <B>image</B> style handles input pixels containing a grayscale or color palette
value. Thus 2D plots (<B>plot</B> command) require 3 columns of data (x,y,value),
while 3D plots (<B>splot</B> command) require 4 columns of data (x,y,z,value).
<P>
The <B>rgbimage</B> style handles input pixels that are described by three separate
values for the red, green, and blue components. Thus 5D data (x,y,r,g,b) is
needed for <B>plot</B> and 6D data (x,y,z,r,g,b) for <B>splot</B>. The individual red,
green, and blue components are assumed to lie in the range [0:255].
<P>
The <B>rgbalpha</B> style handles input pixels that contain alpha channel
(transparency) information in addition to the red, green, and blue components.
Thus 6D data (x,y,r,g,b,a) is needed for <B>plot</B> and 7D data (x,y,z,r,g,b,a)
for <B>splot</B>. The r, g, b, and alpha components are assumed to lie in the range
[0:255].
<BR><HR>
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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
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<LI><A NAME="tex2html1746"
HREF="node70.html">Transparency</A>
<LI><A NAME="tex2html1747"
HREF="node71.html">Image failsafe</A>
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2010-08-17
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