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:mod:`framebuf` --- frame buffer manipulation
=============================================
.. 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, ellipses, polygons, text and even other
FrameBuffers. It is useful when generating output for displays.
For example::
import framebuf
# FrameBuffer needs 2 bytes for every RGB565 pixel
fbuf = framebuf.FrameBuffer(bytearray(100 * 10 * 2), 100, 10, framebuf.RGB565)
fbuf.fill(0)
fbuf.text('MicroPython!', 0, 0, 0xffff)
fbuf.hline(0, 9, 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[, f])
Draw a rectangle at the given location, size and color.
The optional *f* parameter can be set to ``True`` to fill the rectangle.
Otherwise just a one pixel outline is drawn.
.. method:: FrameBuffer.ellipse(x, y, xr, yr, c[, f, m])
Draw an ellipse at the given location. Radii *xr* and *yr* define the
geometry; equal values cause a circle to be drawn. The *c* parameter
defines the color.
The optional *f* parameter can be set to ``True`` to fill the ellipse.
Otherwise just a one pixel outline is drawn.
The optional *m* parameter enables drawing to be restricted to certain
quadrants of the ellipse. The LS four bits determine which quadrants are
to be drawn, with bit 0 specifying Q1, b1 Q2, b2 Q3 and b3 Q4. Quadrants
are numbered counterclockwise with Q1 being top right.
.. method:: FrameBuffer.poly(x, y, coords, c[, f])
Given a list of coordinates, draw an arbitrary (convex or concave) closed
polygon at the given x, y location using the given color.
The *coords* must be specified as a :mod:`array` of integers, e.g.
``array('h', [x0, y0, x1, y1, ... xn, yn])``.
The optional *f* parameter can be set to ``True`` to fill the polygon.
Otherwise just a one pixel outline is drawn.
Drawing text
------------
.. method:: FrameBuffer.text(s, x, y[, c])
Write text to the FrameBuffer using 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=-1, palette=None)
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. (If the *palette* is specified then the *key*
is compared to the value from *palette*, not to the value directly from
*fbuf*.)
The *palette* argument enables blitting between FrameBuffers with differing
formats. Typical usage is to render a monochrome or grayscale glyph/icon to
a color display. The *palette* is a FrameBuffer instance whose format is
that of the current FrameBuffer. The *palette* height is one pixel and its
pixel width is the number of colors in the source FrameBuffer. The *palette*
for an N-bit source needs 2**N pixels; the *palette* for a monochrome source
would have 2 pixels representing background and foreground colors. The
application assigns a color to each pixel in the *palette*. The color of the
current pixel will be that of that *palette* pixel whose x position is the
color of the corresponding source pixel.
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 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.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 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.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
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