Enhance move and rotate tools to facilitate aligning multiple exposures
Submitted by David Biesack
Link to original bug (#650773)
Description
When you wish to do HDR on photos taken without a tripod (or for various other image merge operations), it is important to first align the multiple exposures. Alignment often requires very fine movement and rotation. I start by opening the images in layers, changing the opacity of one layer so I can see where they are misaligned.
The existing Move (M) and rotate tools (Shift-R) help, but have some flaws: When you create guides or change the opacity of a layer, once you start the rotate tool, the opacity reverts to 100% and guides are hidden. Thus, rotating becomes a guessing game.
The Align tool only helps with move but it does not help when the images need slight rotation or distortion.
Here are a couple suggestions to facilitate this alignment operation.
- Provide an option to leave the layer's opacity as set and leave guides visible when using the Rotate and Move tools. If guides remained on, I could create a guide line in the reference image, then rotate the second image/layer until the selected image element is lined up with the guide. If opacity were preserved, I could line layers up with the underlying image. Guides would be easier because you don't have to alter transparancy.
The opacity setting is honored when doing a move (or I can use the Align tool), so it is less of a problem there, but it would still be nice to be able to see guides. This could eliminate the need to change opacity: simply hiding the target layer, set a guide in the reference layer, then showing the target layer and move a similar reference point until it matches the guide.
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Provide a way to select a point in the image as the anchor for rotation. Currently, one must glance at the point's x/y coordinates in the message area and remember them, then invoke the Rotate tool (Shift R) and manually type the coordinates into the anchor point. Finally, the tool should remember/save the last anchor point (and the reset button resets them to the center of the image). So, when doing a Rotate, it would be nice to have a button to allow the user to click anchor point in the image (much like selecting colors with the eyedropper)
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better: provide a tool to automatically align/rotate two or more images (or two or more layers). Create four anchor points on the reference image (i.e. by choosing four convenient reference points such as a corner or other spot on the image that will be easy to select on the other image). Then, select the same four reference points (in the same order) on the second image (or layer). Leave the points selected (lie guides) so the user can zoom in and check/compare them for accuracy and drag/move them if they need tweaking. Then, click an Align button and the second image/layer is automatically scaled/rotated to align the four reference points with the first image. This operation should allow repeating on other images/layers - i.e. a typical automatic exposure bracketing image set has three images. An auto-crop option would also be nice, but only necessary if aligning separate images - it's easy to crop n images if if they were opened as layers.
Version: 2.6.11