#2579 ImageDataSource clip was never tested and is upside-down

[Jeremy Faden]

I found this week that the ImageDataSource "clip=T" control was never tested on multiple plots, and didn't properly flip over the top and bottom pixel coordinates. For example,

https://github.com/autoplot/dev/bugs/2024/20240216/pngWithMeta.png?clip=T&plotInfo=0

clips the wrong plot.

[Jeremy Faden]

This is fixed, subtracting the bottom and top from the height to get the position within the QDataSet where the data should be clipped.

Also, I tweak the pixel positions so that a 1-pixel border (the default for das2 and many others) is removed.

Last, the logic which detects a ratiometric-spaced sequence didn't account for monotonically-decreasing set, resulting in improper guesses for initial axis settings. This is corrected as well.

[Jeremy Faden]

This is fixed.

[Jeremy Faden]

See also https://sourceforge.net/p/autoplot/feature-requests/714/