Image

The image style is intendend for plotting 2D images. It may be used for both plot and splot in the form of 3D data (x,y,value) or projected 4D data (x,y,z,value), respectively. It is assumed that in the viewing plane the image data forms an equidistant sampling grid in the viewing plane along two, not necessarily orthogonal, directions. In other words, groups of four adjacent points are assumed to form the same size parallelogram. The variable value in the tuples represent a palette color (gray value) for indexing in the current palette.

The image style will attempt to create a properly positioned and scaled data matrix to match the plot borders for those terminals supporting palettes and images. Such output is efficient and draws quickly. However, when a terminal driver does not support palettes and images, or when image support is not implemented, the image style reverts to drawing filled rectangular boxes for pixels, which is not as efficient. General parallelogram-shaped images currently always have filled parallelograms for pixels.

The coordinate of each data point of an image will lie at the center of a pixel. That is, an M x N set of data will form an image with M x N pixels. This is slightly different than pm3d elements where an M x N set of data will form a surface of (M-1) x (N-1) elements. The scan directions for the image data grid can be any of eight possible combinations.

Here are some specific comments about particular terminal drivers:

x11 and wxt - Pixels are either repeated or decimated to fit the display

     resolution; no other processing (filtering) is done.  Thus, aliasing may
     occur when decimating images having high spatial frequency content.

postscript (pslatex, epslatex, pstex) - Image is copied in its original

     resolution, and sample interpolation is turned off.

png - Output is dependent on the installed version of libgd.

     gd 1.8.4  No truecolor support, but the driver function works.
     gd 2.0.4  Truecolor works, but if truecolor is not selected
               the image comes out blank.
     gd 2.0.9  Truecolor works, non-truecolor also works.

See also rgbimage (p. ).