MJW

There's my plugin, Recolor Using Palette.

Good idea.

You need to do that using a different layer. Layers provide a consistent way of handling that sort of thing, rather than having a myriad of ad-hoc solutions. There are likely plugins to flip the contents of rectangular selections.

EDITED: Sorry. This was an attempt to edit the above comment. Instead, I must have accidentally replied to it. My excuse is I was working on something else at the time, and unlike most people, I can't walk and chew gum at the same time.

Gaussian blurs are more or less the standard blur, and most likely the one people have in mind when they talk about blurring, without any other qualification. True Blur is Ed Havey's attempt to produce an improved version of Gaussian Blur. Keep in mind that the built-in Gaussian Blur has been improved since True Blur was written, so it may include many of True Blur's features. For instance, the current Gaussian Blur allows fractional radii, while the original did not.

Perhaps I'm mistaken, but I believe that's what the Bokeh Blur does. In a simpler form (without the gamma adjustments), it was previously caller Unfocus, or something like that.

Antialiasing for Magic Wand selections would be very desirable. Unfortunately, the Magic Mand only selects whole pixels, as Rick Brewster explained in a 2017 comment.

A variation I'd suggest trying is to use the Texture Shader's Reflection Map (Equirectangular) Clipboard Image Mapping Method, with an equirectangular map in the clipboard. There are lots of equirectangular maps available, such as on the Equirectangular Flickr Group. I demonstrated a variation on this tutorial more years ago than I like to think about. The advantage of equirectangular maps over other methods of doing reflections is they never need resizing to map onto the image, because they represent the complete environment -- essentially a huge sphere surrounding the object. (That's the reason I added the shading mode in the first place. In fact, I think it may have been this tutorial that inspired me to add it.)

From my long-ago days of using PaintShop Pro, I recall a number of uses for modifying selections, such as expanding or contracting by a pixel or so, or -- a favorite of mine -- smoothing the selection boundary.

If I understand what you hope to do, I think it would be difficult. I don't see a good way to transform a single image into one that looks like a long-exposure photo. In a real long-exposure photo, moving objects leave trails of different lengths and directions, depending on their motion. That seems like it would be hard to duplicate.

If the goal is to essentially replace the black in colors with transparency, there are several plugins that will do that, including my Color Clearer. If you want to do something more complex, you'll need to describe what you want in more detail.

If I correctly understand what you're trying to do (which I may not), copy one image to the clipboard, then paste it as a new layer into the other image. Set the Opacity of the top layer to 127. Merge the layers. (The average color will be very slightly off, since 255 isn't evenly divisible by 2.)

Congratulations to, and appreciation for, @Pixey and @lynxster4! Not sure why i couldn't come up with an entry.

I assume you just have the JPEG versions. If it weren't for the JPEG anomalies, I think it might be mostly readable. Especially if you follow Pixey's advice to get copies the blank forms so you know what to expect. It's none of my business, but I do wonder how you ended up with these sorts of photos, but not the to actual documents. It brings to mind scenes from the old 1960s spy shows, where the agent is furtively snapping pictures of the Top Secret documents with a tiny camera.