Rotation user interface

[Ty]

I have recently used Picasa and some other image programs, and I have seen a very excellent paradigm for rotating images. I think it is superior to what is used in XnView, and request that our esteemed code maestro consider implementing it.

When the user selects rotate, the full-sized image remains on the screen. Also onto the screen comes (a) a grid of fine lines that overlays the image, and (b) a slider switch at the bottom. As the user slides the control, the image rotates accordingly. The grid allows the user to align the image perfectly to an edge or some other vertical or horizontal reference. Because the rotation occurs in real time, and the grid allows perfect alignment, this is a very nice system.

For people who scan from a flatbed scanner, being able to easily rotate the image is very important. I don't know if many XnView users require a good rotation tool, but if so, this should perhaps be considered.

[xnview]

Yes, a good feature. You can have almost the same thing by activating the grid before rotate...

[Ty]

Excellent! By turning on the grid, setting the spacing to "50" or so, and then turning on "apply to image" in the rotate dialog ox, one accomplishes exactly the same thing. I will write this good tip into the help file.

If you agree, I think it would still be nice to have the grid/slider switch in the rotate function. But I can accomplish my needs now without out. Thanks!

[helmut]

A possibilty to show/hide the grid during rotation would be a very good improvement.

There are various topics related to rotation, some examples (I guess our librarian XnTriq would have found more than me):
- Showing of grid while rotating the picture
- Rotation based on the horizon line +auto-crop option

[Ty]

Thanks, Helmut. I see there is lots to think about when considering the best way to handle rotation. For a simple but important improvement to the existing method, I agree with you: a check box to turn on the grid, displayed on the "Image > Rotate > Custom" dialog box, would be very nice.

And although "de-skew" is normally used only for b&w images so they can be OCRed, I think the term can be expanded to also apply to color images. "Skewed," in English, means "off center, mis-aligned, crooked, not straight, distorted, twisted," etc., and color images need straightening, aligning, etc., just as much as b&w images. I would say, in fact, that an alignment of a few degrees is more of a "deskew" or "alignment" operation, than "rotatation." Google/Picasa, in fact, has "rotate" and "straighten" as two completely separate and unrelated operations.

[XnTriq]

There are various topics related to rotation, some examples (I guess our librarian XnTriq would have found more than me):

Nope. You're quite a librarian in your own right, helmut.

[Karl02]

The gimp has been using a variable grid for a fine rotation for a long time. However, in the gimp the grid is rotated instead of the image. This is much less computation effort and hence much faster in the preview. The center of the rotation can be selected and the grid can be rotated with the mouse until it alignes with horizontal or vertical edges of the image. Then you can perform a corrective (backward) rotation, i.e. the image is rotated in the opposite direction of the grid.

A similar method (without setting the center of the rotation) would be to draw a line by specifying two points that should be horizontal in the rotated image.

[Karl02]

I'd like to suggest that the 90/180 degree rotations and the flipping/mirroring should also be displayed in this dialog with a preview. Furthermore, the following rotation options should be shown here:

Code: Select all

[ ] use lossless rotation (jpeg)
    [ ] only change EXIF flag

They should be used only for the current rotation. The defaults should be taken from the options in Options -> Browser -> Misc. They should also be displayed as above: The EXIF rotation is a special case of a lossless rotation, so if the lossless rotation is unchecked, the EXIF rotation option should be deactivated.