From: "Ara.T.Howard" <ahoward@...>
Date: 2004-05-20T12:38:48+09:00
Subject: Re: RMagick jp2 problem

On Thu, 20 May 2004, Tim Hunter wrote:

> On Wed, 19 May 2004 07:19:29 -0600, Ara.T.Howard wrote:
> 
> > On Wed, 19 May 2004, Tim Hunter wrote:
> > 
> >> On Tue, 18 May 2004 21:04:26 -0600, Ara.T.Howard wrote:
> >> 
> >> > yes.  this worries me - it's as if the ImageMagick binding to the
> >> > jasper lib is incorrectly dealing with compression/quality...  as i
> >> > said before, the jasper binary handled perfectly and i get ZERO
> >> > differences when comparing the bands of a tiff image and one converted
> >> > via tifftopnm/jasper...
> 
> Ara, I received your email at my home address but my reply to your .gov
> address bounced(?). Anyway, the ImageMagick developers say that
> 
> convert -quality 100 image.tif image.jp2

yes - i've done this but can subseqently show a diff of the bands using envi
(rsi inc.) or imgcmp (which ships with jasper) - it's bizarre: for the most
part the diff shows all zeros (no difference) but then 20 or 20 pixels will be
different...  at this point this discussion is well off topic but i do have
ONE more RMagick specific question to ask:

what is the most __effecient__ (we are dealing with HUGE images) to compare
the raw pixel values of two images using RMagick, eg (not efficient psuedo
code).

  tiff_pixels = Image.get_pixels
  jp2_pixels = Image.get_pixels

  i = 0
  tiff_pixels.each do |pixel|
    raise "diff @ #{ i } " unless pixel = jp2_pixels[i] 
    i += 0
  end

thanks again.

-a
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