* waveshare2in13v2: Populate bounds only once
The forthcoming introduction of image orientation will make the
computation slightly more complicated. The bounds are fixed during the
lifetime of a "Dev" instance, so it's better to retain them.
* waveshare2in13v2: Make sending image part of drawOpts
* waveshare2in13v2: Unexport drawSpec members
The members of the "drawSpec" structure are only for internal use, so
rename them to start with a lower-case letter.
* waveshare2in13v2: Implement support for rotating image
A new option named "Origin" controls which of the four corners of the
display should be used as the (0,0) position for the image. The
in-memory buffer is kept in logical orientation. The actual rotation
happens only when sending updates.
By aligning the buffer accordingly the code is already prepared for
a more efficient sending of image data for the "TopRight" and
"BottomLeft" origins. See the TODO comment on "drawSpec.BufferDstOffset"
for details.
Signed-off-by: Michael Hanselmann <public@hansmi.ch>
When the destination rectangle didn't start at (0,0) or cover the whole
display the Dev.Draw function would continue to update the display in
full. Obviously that didn't result in a good output.
This change updates the drawing logic to only update the affected area
(aligned to whole bytes on the horizontal axis) and limits the amount of
transferred data to the minimum needed to cover the destination
rectangle.
The calculation of the various offsets as well as the function sending
the image data are written to support unittesting.
Signed-off-by: Michael Hanselmann <public@hansmi.ch>
Dev.Clear: Avoid writing one beyond the end of the line. Also build the
row data only once before sending it for each line.
Dev.Draw, Dev.DrawPartial: Deduplicate logic for iterating over pixels
and simplify it such that a whole row of bits is built before sending
them in one go.
Tested using a Waveshare e-Paper 2.13in V2 display.
Signed-off-by: Michael Hanselmann <public@hansmi.ch>
hansmi