David Fanning wrote:
>
> Actually, I found that it works correctly if I just set
> the Bits_per_Pixel keyword on the DEVICE command to 8.
> (Which is what I would expect to have to do given the
> numbers you use in your image.) But why this should
> be so is a mystery to me. :-(
>
> Cheers,
>
> David
>
> P.S. I don't have time to pursue it this week, but
> I am curious if anyone else has some time.
Thanks, David, for looking into this.
Well, I played with TV a little more, andgot an idea what's going on
here.
From the following code I get the impression that the number of columns
in an array must be an integer multiple of 8/Bits_Per_Pixel to get a
correct PostScript output. ( I know that I would use a setting of
Bits_Per_Pixel=8 for those data, but that's not the point. )
;-- cut here ---
titles = ['nine', 'eight', 'seven', 'six', 'five', 'four', $
'three', 'two', 'one']
columns = [9, 8, 7, 6, 5, 4, 3, 2, 1]
bitsperpixel = [1, 2, 4, 8]
; some test data
image = [$
[ 255B, 179B, 130B, 165B, 120B, 85B, 97B, 151B, 144B],$
[ 102B, 102B, 0B, 124B, 179B, 119B, 118B, 154B, 124B],$
[ 9B, 91B, 35B, 89B, 191B, 82B, 94B, 169B, 31B],$
[ 41B, 90B, 66B, 74B, 151B, 76B, 58B, 142B, 0B] ]
FOR f = 0, 3 DO BEGIN
filename = 'bpp' + StrTrim(String(bitsperpixel[f]), 2) + '.ps'
; set the plot position and ranges
Set_Plot, 'ps'
DEVICE, Filename=filename, /Landscape, /Color, $
BITS_PER_PIXEL=bitsperpixel[f]
position = [0.1, 0.1, 0.9, 0.9]
xsize = (position[2] - position[0]) * !D.X_VSize
ysize = (position[3] - position[1]) * !D.Y_VSize
xstart = position[0] * !D.X_VSize
ystart = position[1] * !D.Y_VSize
; use an inverted color table
Loadct, 0
Tvlct, r, g, b, /GET
Tvlct, Reverse(r), Reverse(g), Reverse(b)
; plot the image
FOR i = 0, n_elements(titles)-1 DO BEGIN
IF i GT 0 THEN Erase
TV, image[0:columns[i]-1, *], xstart, ystart, XSize=xsize,
YSize=ysize
Plot, [1], /nodata, /noerase, position=position, color=255, $
title=titles[i], $
xstyle=1, xrange=[0, columns[i]], $
ystyle=1, yrange=[0, (size(image))[2]]
ENDFOR
DEVICE, /Close
ENDFOR
END
;-- cut here ---
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