TEXT is used to add a permanent annotation text to an image by ``poking'' pixel values to render the text.
The coordinates (X0=, Y0=) give the location in pixels of the upper left-hand corner of the text box. You can compute centering of a string using the cell size and the number of characters in the string. The TEXT= keyword is used to give the text string to embed, but if omitted the program will prompt for the input string. The text may include any valid ASCII keyboard characters.
Text is embedded on the image as a string of 8x11-pixel ASCII characters by changing the data values of the pixels to 32766. The height of an uppercase M is 10 pixels height of a lowercase x is 6 pixels. Each character cell has 1 pixel of white space between it and the surrounding characters, and one pixel of white space below for descenders (e.g., on y and g). The size of the text may be scaled larger using the SCALE= keyword.
Data pixels under the characters proper are lost, but data between character pixels is untouched. If FILL=1 is given, however, the inter-text pixels are set to 0.0 This provides a way of ``boxing and filling'' the text so it does not conflict with background data.
The ROT keyword is used to rotate the text, in increments of 90 degrees. Since we are using a simple text rendering, odd angles do not work satisfactorily.
Note that TEXT makes PERMANENT changes to the data values in the
image being annoted. To make only temporary labels (drawn on the image
display's ``vector'' plane, not by changing image pixels proper), see the
TVPLOT command.