You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
circuitpython/docs/library/framebuf.rst

163 lines
5.7 KiB

:mod:`framebuf` --- Frame buffer manipulation
=============================================
.. include:: ../templates/unsupported_in_circuitpython.inc
.. module:: framebuf
:synopsis: Frame buffer manipulation
This module provides a general frame buffer which can be used to create
bitmap images, which can then be sent to a display.
class FrameBuffer
-----------------
The FrameBuffer class provides a pixel buffer which can be drawn upon with
pixels, lines, rectangles, text and even other FrameBuffer's. It is useful
when generating output for displays.
For example::
import framebuf
# FrameBuffer needs 2 bytes for every RGB565 pixel
fbuf = FrameBuffer(bytearray(10 * 100 * 2), 10, 100, framebuf.RGB565)
fbuf.fill(0)
fbuf.text('MicroPython!', 0, 0, 0xffff)
fbuf.hline(0, 10, 96, 0xffff)
Constructors
------------
.. class:: FrameBuffer(buffer, width, height, format, stride=width)
Construct a FrameBuffer object. The parameters are:
- *buffer* is an object with a buffer protocol which must be large
enough to contain every pixel defined by the width, height and
format of the FrameBuffer.
- *width* is the width of the FrameBuffer in pixels
- *height* is the height of the FrameBuffer in pixels
- *format* specifies the type of pixel used in the FrameBuffer;
permissible values are listed under Constants below. These set the
number of bits used to encode a color value and the layout of these
bits in *buffer*.
Where a color value c is passed to a method, c is a small integer
with an encoding that is dependent on the format of the FrameBuffer.
- *stride* is the number of pixels between each horizontal line
of pixels in the FrameBuffer. This defaults to *width* but may
need adjustments when implementing a FrameBuffer within another
larger FrameBuffer or screen. The *buffer* size must accommodate
an increased step size.
One must specify valid *buffer*, *width*, *height*, *format* and
optionally *stride*. Invalid *buffer* size or dimensions may lead to
unexpected errors.
Drawing primitive shapes
------------------------
The following methods draw shapes onto the FrameBuffer.
.. method:: FrameBuffer.fill(c)
Fill the entire FrameBuffer with the specified color.
.. method:: FrameBuffer.pixel(x, y[, c])
If *c* is not given, get the color value of the specified pixel.
If *c* is given, set the specified pixel to the given color.
.. method:: FrameBuffer.hline(x, y, w, c)
.. method:: FrameBuffer.vline(x, y, h, c)
.. method:: FrameBuffer.line(x1, y1, x2, y2, c)
Draw a line from a set of coordinates using the given color and
a thickness of 1 pixel. The `line` method draws the line up to
a second set of coordinates whereas the `hline` and `vline`
methods draw horizontal and vertical lines respectively up to
a given length.
.. method:: FrameBuffer.rect(x, y, w, h, c)
.. method:: FrameBuffer.fill_rect(x, y, w, h, c)
Draw a rectangle at the given location, size and color. The `rect`
method draws only a 1 pixel outline whereas the `fill_rect` method
draws both the outline and interior.
Drawing text
------------
.. method:: FrameBuffer.text(s, x, y[, c])
Write text to the FrameBuffer using the the coordinates as the upper-left
corner of the text. The color of the text can be defined by the optional
argument but is otherwise a default value of 1. All characters have
dimensions of 8x8 pixels and there is currently no way to change the font.
Other methods
-------------
.. method:: FrameBuffer.scroll(xstep, ystep)
Shift the contents of the FrameBuffer by the given vector. This may
leave a footprint of the previous colors in the FrameBuffer.
.. method:: FrameBuffer.blit(fbuf, x, y[, key])
Draw another FrameBuffer on top of the current one at the given coordinates.
If *key* is specified then it should be a color integer and the
corresponding color will be considered transparent: all pixels with that
color value will not be drawn.
This method works between FrameBuffer instances utilising different formats,
but the resulting colors may be unexpected due to the mismatch in color
formats.
Constants
---------
.. data:: framebuf.MONO_VLSB
Monochrome (1-bit) color format
This defines a mapping where the bits in a byte are vertically mapped with
bit 0 being nearest the top of the screen. Consequently each byte occupies
8 vertical pixels. Subsequent bytes appear at successive horizontal
locations until the rightmost edge is reached. Further bytes are rendered
at locations starting at the leftmost edge, 8 pixels lower.
.. data:: framebuf.MONO_HLSB
Monochrome (1-bit) color format
This defines a mapping where the bits in a byte are horizontally mapped.
Each byte occupies 8 horizontal pixels with bit 0 being the leftmost.
Subsequent bytes appear at successive horizontal locations until the
rightmost edge is reached. Further bytes are rendered on the next row, one
pixel lower.
.. data:: framebuf.MONO_HMSB
Monochrome (1-bit) color format
This defines a mapping where the bits in a byte are horizontally mapped.
Each byte occupies 8 horizontal pixels with bit 7 being the leftmost.
Subsequent bytes appear at successive horizontal locations until the
rightmost edge is reached. Further bytes are rendered on the next row, one
pixel lower.
.. data:: framebuf.RGB565
Red Green Blue (16-bit, 5+6+5) color format
.. data:: framebuf.GS2_HMSB
Grayscale (2-bit) color format
.. data:: framebuf.GS4_HMSB
Grayscale (4-bit) color format
.. data:: framebuf.GS8
Grayscale (8-bit) color format