On Mon, 13 Aug 2007 13:36:05 +0200, Raphaël Quinet <raphael@xxxxxxxx> wrote:> On Mon, 13 Aug 2007 07:10:30 -0400, Robert L Krawitz <rlk@xxxxxxxxxxxx> wrote:> > Would "Use existing image quality settings" be a better name for this?> > I considered naming this option "Use original quality settings", but> one thing that I forgot to mention in my previous messages is that> it is possible to write a script or plug-in that attaches different> quantization tables to any image. [...]
Although I was a bit reluctant to do this, we could try to change thename of this option to "Use original quality settings" or "Use qualitysettings from original image" or something like that. This wouldrequire several changes in behavior explained below. This new meaningmay not be appropriate if other quantization tables than the originalones are attached to the image, but if we consider that usage to be anexception, then maybe we can "optimize for the common case" if thiscould make the option more understandable. Anyway, if we want tochange that string, then we have to reach a consensus on that in thenext few hours and make sure that it will not change again until GIMP2.4 is out. We should be in string freeze now.
If we change the label, this also changes the meaning of the optionand this will require some changes to the code:
- Currently, "Use custom quality settings" is only available when the quantization tables are non-standard ones. If the tables can be generated by the IJG JPEG library, then the option is grayed out because the user can get the same table with the existing "quality" slider (and that slider is already set to the right value if the quality of the original file is better than the user's default). If that option is changed to mean "I want the same settings as the original image" instead of "I want to use some non-standard tables", then that option should always be available even if the original image used standard quantization tables.
- Enabling that option should not only change the quality slider, but it should also change the choice of subsampling parameters, even if the chroma subsampling in the original image is not as good as the user's defaults (i.e., if the default is 1x1 and the original image used the lower quality 2x2 or 2x1). This would ensure that all significant parameters from the original image are re-used when saving. Note that it would be a one-way change: enabling the option "Use original quality settings" would change the subsampling parameters, but changing the subsampling parameters later would not disable the option (unlike what is done when the quality slider is moved).
- Optionally, the usage (or not) of optimized Huffman tables could be detected in the original image and re-used when saving. I think that it would be better to leave it always enabled (always optimize) but if we want to be as close as possible to the original image, then we could disable the optimization if the original image was not optimized.
Implementing these changes would be easy (except for the last one,maybe) and I know exactly what would have to be be changed so the codeitself is not an issue here. But we should quickly decide what thisoption should mean. I like the current meaning ("custom tables") butsome of you think that it would be easier to understand somethingreferring to the original quality settings. If we can reach a quickagreement on what is better (considering the differences explainedabove) and if it is not too late for 2.4rc1, then maybe I could changethat option.
-Raphaël_______________________________________________Gimp-developer mailing listGimp-developer@xxxxxxxxxxxxxxxxxxxxxxxxxxx://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
