Bug Hunting Session
Bug 76931 - Slideshow at 100% zoom factor
Summary: Slideshow at 100% zoom factor
Status: NEW
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: Impress (show other bugs)
Version:
(earliest affected)
4.2.0.2 rc
Hardware: Other All
: medium enhancement
Assignee: Not Assigned
URL:
Whiteboard:
Keywords:
Depends on:
Blocks: Slide-Show Impress-Images ImpressDraw-Enhancements
  Show dependency treegraph
 
Reported: 2014-04-02 07:14 UTC by narayanaras
Modified: 2019-01-11 11:48 UTC (History)
2 users (show)

See Also:
Crash report or crash signature:


Attachments
Shows how the projected GUI gets blurred (421.52 KB, application/zip)
2014-04-08 07:08 UTC, narayanaras
Details

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Description narayanaras 2014-04-02 07:14:56 UTC
I make a lot of presentations by taking screenshots of GUIs (or their parts), and annotating them.

The images look crisp only when-
(a) the screenshot is pasted at 100%, and
(b) the slide is viewed at 100%.

But since the slideshow mode of Impress does not have a 100% zoom mode.
It has either "full screen" mode or "window" mode.

It is virtually impossible to adjust the window size so that the image is rendered precisely at 100%. While adjusting the window size manually, we never know whether we are below 100% or above 100% magnification.

I think this would be a fairly regular use case.

Desired:
Please provide a slideshow setting where the presentation is made at 100% zoom factor.
Comment 1 sophie 2014-04-02 12:22:54 UTC
Hi, did you try to format the screen in Format > Page > Page tab, in the Format drop down list, you can change the screen size, and in the same way the width and height of the diapo - Sophie
Comment 2 narayanaras 2014-04-02 13:04:45 UTC
Hi

I tried the menu you indicated, but didn't find a solution.

IINW the control you mention sets the CANVAS size, but does it ALSO change the WINDOW size of Impress in the slide show mode?

Regardless of the actual size of the canvas, I need to project the slide at 100% zoom.

So for example, if my canvas size is 3"x4", my window size also has to be the EXACTLY the same during the slide-show mode. Logically I cannot select a paper size that is physically larger than my monitor screen.

But the question remains: How do I set the window size at 100%?
Comment 3 Robinson Tryon (qubit) 2014-04-07 21:39:41 UTC
(In reply to comment #0)
> I make a lot of presentations by taking screenshots of GUIs (or their
> parts), and annotating them.
> 
> The images look crisp only when-
> (a) the screenshot is pasted at 100%, and
> (b) the slide is viewed at 100%.

Hi,

I've tried reproducing your results, and I'm not sure I see what you're talking about. Could you please attach an image file and an ODP file that uses the image that demonstrates the scaling issues?

It's possible that our scaling algorithms could be improved...that might help to address the problem in a more complete way.
Comment 4 narayanaras 2014-04-08 07:08:01 UTC
Created attachment 97059 [details]
Shows how the projected GUI gets blurred

The zip contains screenshots of the following test cases:

1. Screenshot in slide, @100% ---------------------->(in "Normal" mode)
2. Slideshow @fullscreen----------------------------> Note that it is blurred
3. Slideshow in window (smaller than original)------> This too is blurred
4. Slideshow in window (nearly original size)-------> crisp, but not perfect
4. Slideshow in window (nearly original size-2)-----> Started to blur
5. Slideshow in window (larger than original)-------> Blurred (like full-screen)
Comment 5 narayanaras 2014-04-08 07:35:18 UTC
Actually I think the scaling algorithm is OK. 

IINW even with the best algorithm, we cannot avoid SOME amount of blurring when a raster image is scaled. So the trick is to project it at 100% in slide show mode, to eliminate any blurring.

Now I do understand that this idea is not compatible with the full-screen projection, where the image will be necessarily magnified. But Impress offers a special slideshow mode in Windows. 

Here are the steps to experience what I mean:

1. First, start an odp file with a small page size (say A5).
   (This allows you to resize the window in a wider range to dramatically demonstrate my point.)

2. Take a screenshot and paste it in the odp file.
   Now we are ready for the experiment.
   Our aim is to reproduce a crisp screenshot even in the slideshow mode.

3. Select the "Slideshow >Slide show settings..." menu option.

4. In the dialog that pops up, go to the "Type" section (in the middle), and select the "Window" radio button. Click OK.

5. Now close the panes on both sides, so that only the main window remains visible. This will allow us to see the effect properly.

6. Press F5 to start the slideshow. The screenshot will be rendered in the window.

7. Change the Impress window size and see the effect on the crispness of the screenshot.

We see that the screenshot is crisp when it is rendered at its original size (100%). This is seen only at a particular size of the window. As we make the window smaller or larger, the screenshot becomes blurred progressively.

I carried out the above experiment, and took screenshots of what I see.
I posted those screenshots just before writing this message.

Note that I used the window slideshow mode just because I can vary the magnification of the projected slide by changing the window size. But my suggestion is NOT limited to "slideshow in window" mode.

I would like to have a slideshow option where the projection is locked to 100%.
It may be in full-screen mode or window mode.
* In full-screen mode, the projection would be in center, and the outer areas on all sides would be left blank
* In windows mode, Impress would decide the window size that gives 100% magnification (which means the user cannot control it)
Comment 6 Robinson Tryon (qubit) 2014-04-08 13:19:43 UTC
(In reply to comment #0)
> The images look crisp only when-
> (a) the screenshot is pasted at 100%, and
> (b) the slide is viewed at 100%.
> ...
> Desired:
> Please provide a slideshow setting where the presentation is made at 100%
> zoom factor.

Testing with the provided images, I agree that the images are indeed most crisp when at 100% zoom, and have the quality drop-off quickly when scaled either up or down.

Seems like an interesting use-case for Impress.

Status -> NEW
Severity -> enhancement