Replacement for 'Set Selection Size'...

Ideas for improvements and requests for new features in XnView Classic

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Olivier_G
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Replacement for 'Set Selection Size'...

Post by Olivier_G » Mon Apr 04, 2005 11:01 pm

As far as I understand: the 'Set selection size' feature has been added in order to facilitate the preparation of a photography for prints of specific sizes. It takes into account the selected size and the dpi information embedded in the file (which can be modified to whatever you want).

I believe that it is not the right way to do the job...

A bit of technical background first:
- dpi (dot per inch) embedded into the file is nothing but a (useless) suggestion.
- real dpi = (real linear size)/(real linear number of pixels). Therefore when you decide to print your 5MP image in A4, 10x15, etc... the embedded dpi is not even taken into account.
- most printing systems use 300dpi which is generally considered as the maximum really useful value. You can also get good results with 180dpi and more (especially on large formats, as you look from further away).
- when you send an image to a printing system, it will interpolate automatically to match the hardware dpi. Some drivers use a bad interpolation algorithm which can lead to pixelisation ('nearest neighbour', just as with my Epson 790), most use a good interpolation (bilinear, bicubic, etc...) and some Pro equipment use very high quality interpolation that can't be matched by software even like Genuine Fractals &Co.

First conclusions:
- the embedded 'dpi' info shouldn't be used.
- using a given value (like 300dpi or whatever) is not really appropriate.
- showing the real dpi based on print size and image dimensions would be more appropriate (+colors like: Red below 180dpi, Orange between 180 and 240dpi, Yellow between 240 and 300dpi, Green above).
- Therefore you should be able to resize the selection (the ratio will be fixed) in order to choose what you want from the original picture and the 'real dpi' information will be updated accordingly.
- After cropping, the image should be resized to follow some rules set in the options: the dpi to follow ('no change' or a fixed value +[always]/[increase only]/[reduce only]) and the resizing algorithm (nearest neighbour, bilinear, bicubic, lanczos, etc.. + sharpen option).

With a default value of "300dpi[always]"+Lanczos, the user would just have to select the size of the output, move/resize the selection to his liking while checking the quality color (real dpi) and apply => the resulting image would immediately have the right dimensions.

I will try to come up with a good solution to incorporate this method within the ratio selection feature and simplify the whole process.
Meanwhile, I didn't find the current implementation really usable.

Olivier
Last edited by Olivier_G on Fri Jul 28, 2006 9:52 am, edited 1 time in total.

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helmut
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Post by helmut » Thu Apr 07, 2005 8:13 am

Thank you very much, Olivier, for raising this topic.

Maybe you remember my note in the topic "Suggestion to Selection ratio":

"I don't like the Selection size, either, and have never used it. According to Pierre it's needed for printing images, but I think it's only a workaround for some limitation in printing."

I think to find a solution we have to first understand what the benefit and usage of "Selection size" and "dpi" is:

"dpi" is "dots per inch" and is an indicator for the image's real size. The dpi information is needed whenever a conversion from pixel dimensions to "real world dimensions" (inch, centimeter, ...) has to be done.

From what I can see the main area for such a conversion is printing. If I understand "Selection size" right, you select a specific part of the image and then print it using the setting "DPI" as size. This is a possible way, but I think a much better and more intuitive way is to provide a print preview and have various options to vary the size. XnView can do this, already. If other software (or direct printing?) is used, a correct dpi info and size might be needed, but any good software used for printing should support both previewing and scaling.

So until now I cannot see a real benefit from the "Selection size" and think that it can be simply removed. This would make the user interface clearer and especially novice users wouldn't get confused by selection ratio and selection size.

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Olivier_G
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Post by Olivier_G » Thu Apr 07, 2005 9:21 am

helmut wrote:From what I can see the main area for such a conversion is printing. If I understand "Selection size" right, you select a specific part of the image and then print it using the setting "DPI" as size. This is a possible way, but I think a much better and more intuitive way is to provide a print preview and have various options to vary the size. XnView can do this, already.
The idea behind "Set selection size" may actually be useful if you want to 'prepare' several images for printing on another system (a friend's printer, your local printing service or over the Internet) in order to be in control (be it for filesize or quality issues).

I think we can come up with something both easy to use (for our Mums&Dads) and very efficient/good (for experts).

Olivier

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update...

Post by Olivier_G » Sat Jul 16, 2005 1:30 pm

I have a first proposal:
- Remove 'set selection size menu'
- Available sizes would appear instead in sub-menus of 'set selection ratio' in their corresponding ratio (it should still be possible to choose a ratio without precising any size)
- The size selected should appear just above the selection and it's color would indicate the 'quality status' (real calculated dpi) updated in real-time (ie: Red below 180dpi, Orange between 180 and 240dpi, Yellow between 240 and 300dpi, Green above - the dpi value could be shown as well).
- Below the normal 'Crop', there should be 'Crop and resize' that would crop the selection +resize to its final printing size based on the 'Printing DPI' set in the Options (size x dpi) +dpi of the image set to this value.

Example: let's say that I use a 3MP image from a digicam and want to print a 11x15cm print of a selected area ('printing dpi' set to the default 300dpi value)
- Choose Set selection size > 4:3 > 11x15cm
- "11x15cm" appears above the selection
- It will be green, until I select too small a detail for this print size
- I select 'Crop and resize' and get the cropped image at the appropriate size (1795x1346 pixels) and dpi (300dpi) for printing.

Such a system would be very useful when preparing several images for the same printing size, especially if they are from different sources (ie: different image sizes). It will also give you optimized files (size/quality) and allow you to check in realtime that the resolution is enough for the printing size selected.

Olivier

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Post by marsh » Fri Aug 05, 2005 1:04 am

It would be logical to expect 'selection size' to match the display units used(pixels, cm, inches).
Perhaps replacing current menu with the following function would help:
'Set Custom Selection size' (using the selected display units- pixels by default).
This function could make it easier to copy and paste a specific area between multiple tabs (by keeping same proportion and dimensions).

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Post by Olivier_G » Fri Jul 28, 2006 1:17 am

Updated proposal: Show standard sizes for selected ratio with color indicators (+real dpi)
Image
Click to see full image (57KB)

Once a ratio is chosen, the user would freely define selection's size and get feedback on quality, based on real output dpi. Those dpi would depend on selection size in pixels and output size: XnView would show several standard output sizes for the selected ratio.
Quality range colors could be: >300dpi = Very good; 240->300dpi = Good; 180->240dpi = Acceptable; <180dpi = Poor

In the above example, the user would know that he has really plenty to get a 10x15cm print, enough for a 20x30cm print (but should be carefull not to reduce selection too much) and that it would be more difficult for a 30x45 print (actually, large sizes should not be in bold as they are observed from a greater distance: the dpi rule relax somewhat). Quality color and dpi would be updated real-time based on selection size.

How it would work:
- Based on measurement system chosen ('cm' or 'inches' with option to show pixels and/or distance in status bar), XnView would list standard output sizes for each selected ratio.
- Real dpi (and quality color) for each output standard would be calculated based on 'Selection's length in pixels'/'Output's length converted to inches'.
- You should be able to turn that system On/OFF with menu "Selection - Optimized for prints".


Now... there is a second part that allows the user to get optimized images for printing:
Once the user has chosen the selection, clicking 'crop' (with Selection - Optimized for prints = ON) would open the following dialog:

Code: Select all

Print size? |10x15cm|v|
            |20x30cm|
            |30x45cm|
            |Custom |  => [ ] x [ ] (note: entering one value determines the other based on ratio)
Then, the cropped picture would be resized based on the options 'output dpi' and 'resize method':
- 'Output dpi': EXIF or User specified (+option to automatically replace the previous EXIF on save)
Default would be: User specified=360dpi [don't save] (because lots of Epson printers have bad resizing and work natively at 720ppi...). This dpi setting would also be used for distance in status bar.
- 'Resize method' and whether it should be applied 'to reduce only' or 'always' (default: Lanczos & always).

With that function, the user would be able to crop while checking the quality required for prints and get images of the right size... :D
Olivier

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Post by Olivier_G » Fri Oct 13, 2006 4:05 pm

I update this thread since I am in KISS berserk mode and it would allow to remove that dreadful 'set selection size' menu completely.
Too complex for 1.90 implementation, but I would like to hear more feedback/support, please.
Olivier

aare07
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Set Selection Ratio

Post by aare07 » Sun Apr 15, 2007 9:04 pm

May i post my opinion to this topic: I use the selection ratio to prepare the pictures for the web. I might be an better command, but i have found only this way to crop the pictures to an specific size.

I also find the actual command limited. But, please do not remove it from the programm, instead improve it:
I think it is not possible to have every needed ratio set in the menu.
It woul be more useful, to have a few common ration fix in the menu (i.E 14:3, 5:4, A4) and 3 custom definable ratios. There it would be possible to set the ratio in an way 6:5 or in pixels 155 x 100. This is very handy to prepare images to crop and resize to an defined web size.

The same also for the meny "set selection size"

PS: It is one of the only functions i am using still in gimp, fixed selection size or ratio set by the user in pixels.

PS: Thanxs for that grat prtogramm !
Greetings Aare
Aare

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