Originally, the only (non-debug) way to make an LFO calculate its value
was to associate it with a playing synthesizer.
This posed a problem for LFOs that had "power on values" other than 0,
and where the value was used other than to internally drive a note
property.
Now, an initial, possibly non-zero value is calculated at object
construction time:
```py
>>> l = synthio.LFO(offset = 1)
>>> l.value
1.0
```
Note that this happens just once at construction; it does not happen when
updating LFO properties:
```py
>>> l.offset = 2
>>> l.value
1.0
```
This can perform arbitrary channel mixing between two images.
Alpha blend & maximum functions are demonstrated in the test.
However, it should make most of the usual photo editing blends
possible. (for dissolve, fill a mask bitmap with random values,
which may be expensive to do from circuitpython code; we can
specifically accelerate it if we need to)
morph9 is a form of morph which performs 9 different convolutions,
like a version of mix where each coefficient is a (2n+1)x(2n+1) matrix.
Most use cases are covered by morph-then-mix, but some advanced operations
may be more efficient to implement via morph9.
This allows operations between channels in an image. It can be used for
the following use cases:
* Conversion to B&W or sepia
* Adding color casts
* Mixing or swapping arbitrary channels
* Inverting or scaling arbitrary channels
bitmapfilter.morph is taken from openmv's imlib.
It is substantially faster than blur/sharpen implemented in ulab,
by up to 10x. It also avoids making many allocations.
This function in standard Python is a building block for custom REPLs:
```python
from codeop import compile_command
print("Repl in (Circuit-)Python")
ns = {}
PS1="<<< "
PS2=",,, "
command = ""
while True:
line = input(PS2 if command else PS1)
if command:
command = command + "\n" + line
else:
command = line
try:
if (code := compile_command(command)):
command = ""
exec(code, ns)
except Exception as e:
command = ""
print(e)
```
Previously, negative amplitudes were clamped to zero.
Now, they are allowed to range from -ALMOST_ONE to +ALMOST_ONE.
This is useful in certain circumstances, such as using synthio
to create CV-like outputs that can be positive or negative, by
using the amplitude property of the note.
This enables the specific use case of checking whether a note's release
phase has ended, but is also potentially useful to implement a sort of
"voice stealing" algorithm in Python code, which can take account of
the note's envelope state as well as other factors specific to the
program.
Apply envelope & panning after biquad filtering.
This may fix the weird popping problem. It also reduces the number
of operations that are done "in stereo", so it could help performance.
It also fixes a previously unnoticed problem where a ring-modulated
waveform had 2x the amplitude of an un-modulated waveform.
The test differences look large but it's because some values got changed
in the LSB after the mathematical divisions were moved around.
