On Wednesday 23 August 2006 03:25, Anthony Thyssen wrote: > =?iso-8859-1?q?J=F8rn_Dahl-Stamnes?= on wrote... > > | I use IM to reduce the size of the images I want to display on my > | web-page. Last weekend I shot some pictures from a mountain bike race: > | > | www.dahl-stamnes.net/Foto/show.php?album=Marka_2006_1 > | www.dahl-stamnes.net/Foto/show.php?album=Marka_2006_2 > | > | However, a viewer commented that he though the pictures was not that good > | in quality. He thought he saw to much noice and talked about "aliasing > | artifac" (sp?). > | > | Any comments? > > Well you certainly made it difficult to download the image! > I had to look at the page source to figure out > http://www.dahl-stamnes.net/Foto/img.php?img=20583 > > The image downloaded is a JPEG! Of course the image will be a lower > quality, and contain aliasing artifacts. What does he want?
As a friend of my said it: A high quality picture he can use for his own purpose without having to pay for it, mabe? ;-);-) > If anything it should be even lower quality for web use, with a link to > a larger higher quality, and high bandwidth one, in PNG (only for > specific people like the owner). I use '-quality 75' when creating the images. I did some experiments yesterday with differente value to the -quality option. I made a picture with '-quality 90'. Then I took both images into photoshop and put both images into one (2 layers) and changed the layer mode to difference. I got a complete black image. Doesn't this indicate that there is no difference between the two images? > PS: I would use a tiled watermark, as a centered one may not stop people > grabbing and cropping a relevent part that is not in the center of the > image. I have tried it but people thought it was to disturbing. > Actually I thought it came out pretty good. Ask the person for a > specific example of the low quality aspect. > > Also in what format did you get the photo? and was it high quality? > Compare against his specific example of the problem. The original is Canon RAW format (.cr2 files, output from 20D and 30D). The workflow after I have shot some pictures is: * Use Canon's software to view and adjust (lightnes, contrast, color) on the raw pictures. Delete the one that is not worth keeping. * Convert the raw files to jpg. The jpg files are used for the archive program while the raw files are stored for later use. * Add all jpg files into the archive. * Select the pictures in the archive I want to have on my web-page and then create a CSV file containing the names of the files + additional information. * Use my own perl/bash scripts to resize and create thumbnails. The scripts use IM to do this work * Move the resized jpg files to the web-server and update the SQL database with information about the pictures. > Remember every time a JPG image is loaded and saved it degrades. If the > user has done this before passing to you the quality will suffer. I know. > The best source is the exact image generated by the digital camera > without any changes (or even a load an save from a viewer, just plain > file copies) The source which IM use to create the jpg files on my web-server, is the jpg file created from the raw files (the jpg file in the archive). The quality of the jpg is higher than the original file would have been if I shoot in jpg mode (and not raw). -- Jørn Dahl-Stamnes homepage: http://www.dahl-stamnes.net/dahls/ _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
