Re: [BUG] Epson 1640SU, xsane preview problem

From: Oliver Rauch (oliver.rauch@rauch-domain.de)
Date: Thu May 24 2001 - 05:08:36 PDT

  • Next message: Oliver Rauch: "Re: [BUG] Epson 1640SU, xsane preview problem"

    mh wrote:
     
    > Errm, it displays the wanted subpart, but uses the *wrong* preview for this.
    > (I think that's what the original poster was talking about).
    >
    > BTW, this should happen independently of the backend(?):
    > -insert a document and scan a fullsize preview
    > -insert a new document, change the previewsize to A5 e.g.
    > -If you now start a preview scan, the new document is shown for a short moment,
    > but gets immediately replaced with the subpart of the *previous* document
    > (p->filename[0], which is a preview of the first document, and not of the
    > current document in this case)
    > Or is this intended; does one have to scan a fullsize preview first ?

    Hi Michael,

    may be I know what happens.

    The strategy of xsane is:
    - 3 different preview levels available:
    level 0 is full scanner surface
    level 1 is reduced surface, reduced area seleced in preview window
    level 2 is zoomed area (zoom function in preview window)

    - when everthing works like expected then:
    level 0 is done with a low resolution
    level 1+2 are done with a higer resolution
    this means that the qualtiy of level 1 and level 2
    are normaly higher than the quality of level 0

    - xsane does calculate the quality by the resolution
      of the part of the image that shall be displayed

    - when the preview has to be redrawn xsane does load
    the preview image with the higest qualtiy.

    I think what happens is that the level 0 preview
    has a higher quality than the level 1 preview.
    Normally this can not happen because xsane does
    set a higher resolution for the level 1 preview than
    for level 0.
    The epson backend uses a resolution list with
    a strange correction routine that does not
    allow to set exact resolutions (that are
    part of the list).
    The plustek backend defines a range and internally
    selects a suitable value from a list.

    I think in these cases it can happen that the quality of
    level 0 image is the same or higher that the quality of
    level 1 and so the level 0 image is used.

    Please could you test the following:

    edit xsane-preview.c line 2066

        if (quality < min_quality)
        {
          return min_quality;
        }
    change
        if (quality < min_quality)
    to
        if (quality <= min_quality)

    bye
    Oliver

    -- 
    Homepage:	http://www.rauch-domain.de
    sane-umax:	http://www.rauch-domain.de/sane-umax
    xsane:		http://www.xsane.org
    E-Mail:		mailto:Oliver.Rauch@rauch-domain.de
    

    -- Source code, list archive, and docs: http://www.mostang.com/sane/ To unsubscribe: echo unsubscribe sane-devel | mail majordomo@mostang.com



    This archive was generated by hypermail 2b29 : Thu May 24 2001 - 05:18:23 PDT