image limits

[John W. Eaton]

On  8-Feb-2007, Daniel J Sebald wrote:

| Here's something for you to think about.  I don't think there is any
| rush to resolve this, as gnuplot may tweak behavior on images
| slightly (hence labeled experimental in gnuplot's configuration).
| But, if one tries (in CVS) image, the outermost pixels are
| fractionally displayed by the automatic choice of limits.  To
| exaggerate, try
| 
| image([4 5 6; 7 8 9; 0 1 2])
| 
| The array is 3x3 and the limits are chosen as [1:3], which only
| covers the length of two pixels.
| 
| Like I say, gnuplot may be adjusted if there is a discussion about
| any accepted conventions in the graphics community (i.e., start
| image at zero, etc.).

Try this with the current CVS Octave:

  image
  axis ([0, 10, 0, 20])

I think you'll see that the axis limits change, but the full image
remains displayed.  In Matlab, the axis limits correspond to pixel
indices, so changing the axis limits zooms in on the image.  We should
probably do the same.  Are we just not using gnuplot correctly here,
or is this a feature of gnuplot that the axis limits are independent
of the size of the image?

jwe