From:	MERC::"uunet!CRVAX.SRI.COM!RELAY-INFO-VAX" 14-NOV-1992 12:35 14-NOV-1992 12:35:00.00
To:	mlevin@husc8.harvard.edu, info-vax@sri.com
CC:	
Subj:	Re: How do I throw a pixmap up on a DecWindows screen at once?

In article <1992Nov10.202825.17325@husc3.harvard.edu> you write:
#     I am a complete novice to X-windows programming (although I know
#C and unix and VMS systems programming at an intermediate level). I
#need to take a 2-dimensional array of colormap indeces, corresponding
#to a rectangular patch of the screen with pixels of different colors,
#and throw it up as a window on a Ultrix VAX or a VMS Vax with
#DecWindows (no MIT X stuff - just regular out-of-the-box DecWindows)
#from a C program. Something like this:
#display_in_window(array)
#
#short array[X][Y];
#{
#   /* here's the part I'm having trouble with */
#}
#
#where each element of array[][] will be 0 for black, 1 for white, 2
#for green, etc.
#   Is there any code anywhere that will show me how to do this? At
#least a hint as to which routines I should be looking at (I don't have
#a DecWindows manual, but I'll get one if there's no PD code already
#around to do this - what's the proper manual called?). If anyone has
#any helpful suggestions, please email me at mlevin@husc8.harvard.edu.
#

Mike,

What you need to do is two fold

	1) Allocate the colors using the XColor structure like so

		XColor colors[256];

		for (i = 0; i < 256; i++) {
			colors[i].pixel = i;	/* value to reference this color by */
			colors[i].red   = red;	/* RGB value for red */
			colors[i].green = green;/* RGB value for green */
			colors[i].blue  = blue;	/* RGB value for blue */
			colors[i].flags = DoRed | DoGreen | DoBlue;
		}

		XSetColors(dpy, DefaultColormapOfScreen(scr), colors, 256);

	2) Create an XImage structure containing the imagedata where
	   the image data is a array[] of pixel values matching those
	   you setup in the colormap;


	XImage *image;
	unsigned char image_array[90000];	/* 300x300 image */

	/*
	 *	Load image (any way you want)
	 */

	/*
	 *	Create XImage
	 */
	image = XCreateImage(dpy,
			     DefaultVisualOfScreen(scr), /* what is the visual */
			     DefaultDepthOfScreen(scr),	/* how deep is the display */
			     ZPixmap,	/* needed for images made up of pixels */
			     0,		/* offset to start of image */
			     image_array,
			     300, 300,	/* image is 300x300 */
			     8,		/* image is in 8 bit units */
			     300);	/* number of bytes per line */

	3) Put the image to the window you want using XPutImage.

	XPutImage(dpy,
		  window,		/* window to display image in */
		  gc,			/* graphics context */
		  image,		/* XImage to use */
		  0, 0,			/* start at the start of the Image */
		  0, 0,			/* place in window starting at (0,0) */
		  300, 300);		/* image is 300x300 */

This is a simplified example, but should get you started.

--
Patrick L. Mahan

--- TGV Window Washer ------------------------------- Mahan@TGV.COM ---------

Waking a person unnecessarily should not be considered  - Lazarus Long
a capital crime.  For a first offense, that is            From the Notebooks of
							  Lazarus Long