IDL Tutorial 2: Plots and Output Files for Making Hardcopies .. Hence, you need to first start the PS device using the set_plot command, and then use the. SET_PLOT, ‘PS’. This causes IDL to use the PostScript driver for producing graphical output. Once the PostScript driver is enabled via SET_PLOT, the DEVICE. IDL treats the screen as one device and a postscript file (which you can print) as another. You can switch devices with the set_plot command.
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If the image column size is not an sef_plot multiple, extra pixels with a value of are output at the end of each row. The assumption is that you are on a Windows-based machine, but I’ll include some info to help you plot from Linux, below.
MULTI system variable described in more detail in. The page on the right shows an IDL plot printed in “landscape” orientation. You have more options under Linux, but your best bet is set_plof use a program called “gv. True-Color Images A true-color image consists of an array with three dimensions, one of which has a size of three, containing the three color components.
Enabling color also enables the color tables. For example a true-color n by m element image can be ordered in three ways: Many laser il and high-resolution, high-quality photo typesetters support PostScript.
It was produced with the following IDL statements: By convention the first color is always red, the second green, and the last is blue. It sets the default color! Sometimes, set_plor, the default bounding box is inappropriate for the image being displayed.
The third element is the number of rows per page. Otherwise, the internal color tables are not changed. Portrait, non-encapsulated, no color. This offset is always taken relative to the lower left-hand corner of the page when viewed in portrait orientation.
IDL Graphics Devices
If the new device has more colors than the old device, some color indices will be invalid. The height of the picture is stored in s: This happens because IDL moves the origin of the plot before rotating the PostScript coordinate system degrees clockwise for the landscape plot.
Set up IDL to plot an encapsulated postscript file of some chosen name. Unlike monitors where white is the most visible color, PostScript writes black on white paper. The default is to do nothing. The user is required to select the dil manually from the printer dialog.
IDL Tutorial 2 : Plots and Output Files for Making Hardcopies
This causes no problems if the color white is loaded into the last color table entry, otherwise a stripe of the last index number color is drawn to the right of the image. Similarly, when output to an EPS file, this image will swt_plot fill a small portion of the bounding box.
A value of 1 specifies pixel interleaving, 2 is row interleaving, and 3 is image interleaving. To direct graphics output to a PostScript file, issue the command: The first element of!
To pass the RGB pixel values without change, load the red, green and blue color tables with a ramp with a slope of 1. D to reflect the configuration of the new device. This is the preferred method if you are displaying graphics and each color index is explicitly loaded.
Creating PDF Files in IDL
Here is a set of commands to generate an encapsulated postscript file. The case of Device is ignored by IDL. A color index of writes white which is invisible on white paper.
Be careful when switching devices as the number of color indices frequently differs between devices. It also provides several examples of how the PostScript graphics device is used. Set this keyword to indicate that the current contents of the internal color table should be interpolated to cover the range of the newly-selected device. The following example writes a bit image, interleaved over the 3rd dimension, to a PostScript file: TVLCT, [0,0,0], [0,0,0], [0,0,0,] Drawing text or graphics with a color index of 0 results in black, 1 in red, 2 in green, and 3 in blue.
Setting the output color index to 0, the default when PostScript output is selected, writes black. In each case, a different number of bits are used per image pixel. In this case, the same image is reproduced four times. A pseudo-color image is a two dimensional image, each pixel of which is used to index the color table, thereby obtaining an RGB value for each possible pixel value. This method works best when displaying images with continuous color ranges. Vertical offset 5 in.
Set this keyword to set_plof the device’s color table from the internal color table, preserving the current color mapping. These keywords control the position of IDL plots on the page.
Tweak it until you like the plot. Assuming that the previously-selected device’s color table contains M elements, and the new device’s color table contains N elements, then the minimum of M and N elements are loaded.
The following example writes a bit image, interleaved over the 3rd dimension, to a PostScript file:.