Re: [gtk-list] Re: Displaying JPEGs

[john giorgio hart bbk ac uk]

Larry Lee <lclee@primenet.com> wrote:
>IS THIS REASONABLE, OR HAVE I DONE SOMETHING SILLY?

Hiya:) maybe. In drawmap2, you had:

	void
	drawmap2 (GtkWidget *drawing_area)
	{
	    int     x,y;
	    char    buf[3*VMX];

	    for (y=0; y<VMY; y++) {
		char *bp = buf;
		for (x=0; x<VMX; x++) {
		    *bp++ = 0;
		    *bp++ = (VMX-x)*256/VMX;
		    *bp++ = 0;

		    gdk_draw_rgb_image (drawing_area->window,
			drawing_area->style->white_gc,
			0, y, VMX, 1, GDK_RGB_DITHER_NONE,
			buf, VMX);
		}
	    }
	}

So you've got the gdk_draw_rgb_image() inside you inner loop: you're calling
it every time you generate a pixel, rather than every time you finish a line.
I tried moving it out one brace, and I get about 1 sec for 800x600.

You can go a bit quicker still if you render the entire 800x600 image into an
array in your program somewhere, and then do a single call to
gdk_draw_rgb_image(). This gets the time down to about 0.7 secs for me. 

Good luck,

John