Whereas I want it to look something like this
That takes software, and software costs money. Real Photographers™ are used to paying hundreds or even thousands of pounds on lenses and camera bodies (the Canon EOS 5D Mark IV body alone is £3,000 and high-quality lenses go for £1,000). £120 a year for Lightroom and Photoshop, or £105 for the Lightroom 6 download is nothing. I'm not a Real Photographer: for me, software competes with books, movies and CDs. Which is how we consumers do price comparison, but sometimes we miss the point.
My iPhone SE will have cost me a few hundred pounds after the 24-month contract is over. To get the best out of my phone and hence that money, I need to spend a small-ish - compared to the cost of the phone - amount on perspective-correcting software. And I will take more pictures, which is the point of have a camera in my pocket all the time.
So now, look!, I've convinced myself to shell out. I am not tempted to do image-editing on my iPhone. Photos offers basic editing facilities already, and even a quick experiment convinces me that my eyes are no longer young enough to be reliable enough to make those kinds of adjustments. So I’m only going to do stuff on the Mac, or maybe the iPad.
For reasons that have to do with spontenaity, I have SKRWT on my iPad. SKRWT is as good as the reviews say it is. I can transfer pictures to it from my phone using Air Drop. Which is every bit as easy to use as it says it is. So I could do my picture editing on the iPad, and it gives me as large an image as I get from Picasa on the Mac Air. (Just pretend I never said Picasa.)
Now for the Mac Air. SKRWT is iOS-only, but there's something that looks very similar, from DxO Perspective. It gets good reviews, so I installed that to handle the images that are already on the Mac.
This is what DxO can do. Here’s an original…
and here’s a correction using the rectangle tool and some cropping
That was the photograph I wanted. To get that au naturel, I would have needed a medium-format camera, as even a 35mm full-frame / film would not have let me get the whole frontage in at that distance.