On Sat, 3 Nov 2007 00:06:18 +0100, Karl Günter Wünsch <kgw@xxxxxxxxxxxxxxxxxxxxx> wrote:> On Friday 02 November 2007, Raphaël Quinet wrote:> > There are also some improvements for the JPEG plug-in. As I mentioned> > some time ago, I would like to hide the current "quality" slider among> > the advanced options, and replace it by a smaller selection of> > pre-defined quality levels. > [...] every site I post my images to has > stringent restrictions on file size [...]> Having preset quality settings really is no option, it is a major annoyance in > Photoshop new users I spoke to always are struggling with! It looks like what you want is a "Save for Web" feature (especially becauseyou mention posting images to some sites). Photoshop offers two differentways to save a JPEG image: 1) The normal Save assumes that you use JPEG like most other (lossless) image formats. Professional users expect that the image will be saved with a rather high quality, will contain the appropriate color profiles and other metadata related to the image so that it can be integrated in a publishing process and eventually printed. Photoshop allows the user to select quality levels between 0 and 12 (but each of them sets more than just the "quality" because the subsampling parameters are also affected). The lowest level (0) is equivalent to quality 85 in GIMP, and the highest level (12) is somewhere between 97 and 98 in GIMP. But using levels 11 and 12 is not recommended, so the recommended "High quality" level is 10, which is equivalent to quality 93 in GIMP. 2) The Save for Web feature assumes that you will put the image on some web site instead of printing it, so you care more about the size of the file than about its faithful rendering on a printer. Save for Web allows you to remove most metadata from your image and gives you more control over some JPEG parameters that can help you to reduce the size of the file. Among others, it has a slider that goes from 1 to 100 so that you can fine-tune the size/quality and it also has an option that lets you enter the target file size so that Photoshop can select the compression level that brings you as close as possible to this target value. Note that the 1-100 slider in Photoshop is not the same as in GIMP: the corresponding range in GIMP would be 55-98 (approximately). Experienced Photoshop users will select "Save" or "Save for Web" dependingon what they intend to do with the image. The goals are different andalmost mutually exclusive:1) Save: high fidelity for printing, include all metadata, no need for a preview of the JPEG compression quality, no need to estimate the size of the file before saving2) Save for web: focus on the size/quality trade-off, it is important to have a preview and to predict the size of the file, no need for metadata, assume sRGB color profile. Currently, GIMP tries to do a bit of both in the same jpeg plug-in anddoes not do either of them correctly:- For a normal Save, it is a bit stupid to have a quality slider that goes from 0 to 100 if the useful range is only between 85 and 95.- Showing only the quality slider in the default view misleads users into thinking that they only have to play with that value in order to reach a target size for the file. Changing the subsampling parameters can be as important in order to reach the best size/quality ratio.- It is necessary to check or uncheck several checkboxes in order to select if metatada and image thumbnails should be included or not.- Several other checkboxes that are rarely used clutter the list of options. The choice of DCT method and the inclusion of restart markers are special features that are almost never used (or used wrongly). Considering all that, I think that it would be much better to provide asimplified set of choices. Each of them would combine several parameterssuch as quality and subsampling. This would streamline the interface forthe common case for our target users (cfr. GIMP vision). Of course, theadvanced settings would still be available and this would include the oldquality slider if you think that it is useful. But for the kind of usecase that you described, the ability to enter a target size for the filewould be more useful. We could also change the jpeg plug-in so that itremembers if the advanced options are expanded or not, and maybe make itremember that across sessions. So if you insist on using the old qualityslider for each image, you could still do that easily. -Raphaël P.S.: For more information about the mapping between Photoshop and GIMP quality levels, see: http://blogs.gnome.org/raphael/2007/10/23/mapping-jpeg-compression-levels-between-adobe-photoshop-and-gimp-24/_______________________________________________Gimp-developer mailing listGimp-developer@xxxxxxxxxxxxxxxxxxxxxxxxxxx://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
