"Felix E. Klee" on wrote... | Am Mittwoch, 22. März 2006 04:23 schrieb Anthony Thyssen: | > You can control the resize 'bluring' effects from merging pixels by | > using the -filter and -support settings. See | > http://www.cit.gu.edu.au/~anthony/graphics/imagick6/resize/#filters | | Nice overview! | | > By default filter for shrinking images is Lanczos for its speed. | | Is there really any point in having that many filters available when shrinking | an image? AFAICS, there are only two algorithms that make any sense: | | Algorithm A: Remove approximately evenly spaced horizontal and vertical lines | from the image. This algorithm is fast but the result usually is not very | nice. | | Algorithm B: Subdivide the image into squares representing the destination | pixels. Then average the color of the source pixels in each square and | assign the resulting value to the corresponding pixel in the destination | image. The values of pixels that are not completely within a square are | weighted accordingly. This algorithm is slower than A but yields optimal | results, AFAICS. | | So, why those many filters? Which filter corresponds to algorithm B? | Algorthim A is the 'Point' filter, Algorithm B is the 'Box' filter
However just averaging pixels does not always produce a good result as you can for just a small size reducion an original line group then a single averaged line, then another original line group, and so on. The result is not specifically nice for the generic case. The Lanczos and other filters avergae the pixels a little more uniformly producing a better result. However some sharpingening or other smoothing after a resize may improve things. I am not up on this type of thing, and would love others to put in their views mproving image reduction. | > Solutions for that type of problem is to apply some contrast handling to | > attempt to brighten and thicken the lines. My minimal (very minimal) | > notes on this is also on the image resizing page at | > http://www.cit.gu.edu.au/~anthony/graphics/imagick6/resize/#thin_lines | | Thanks, this may come in handy at times. | | > While I don't have any examples or other infomation I would be | > interesting in any solutions you do come up with. | | Well, I guess that we'll not be using ImageMagick's "display" as a viewer in | that particular case. The user interface is a bit arcane for the people | who'll use it. | | > Sorry I can not be much help. | | That's not true. You've raised several interesting issues and you've pointed | me to your site which is certainly a great supplement to the existing | ImageMagick documentation. | | PS: You didn't put the ImageMagick list in CC. If this was an accident, then | let me know, and I'll repost the above reply to the list. Note that I never | sent replies to private messages to mailing lists: Sometimes people may not | want that (although no one ever complained). | It was an accident. I have CC'd this email. I'll let you Cc the previous. NOTE I will not be around from mid next week as I am on a month long European Vacation. Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]> ----------------------------------------------------------------------------- A / \ o `` Impressive... /</ \/|> Obi Wan has taught you well. '' / \ /\ /___\ \ \ -- StarWars ----------------------------------------------------------------------------- Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/ _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
