: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, 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 = framebuf.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=-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.

    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
