docs/library: Add framebuf documentation.

docs/library/framebuf.rst

@@ -0,0 +1,129 @@
+: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 = 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;
+          valid values are ``framebuf.MVLSB``, ``framebuf.RGB565``
+          and ``framebuf.GS4_HMSB``. MVLSB is monochrome 8-bit color,
+          RGB565 is RGB 16-bit color, and GS4_HMSB is grayscale 4-bit color.
+          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's utilising different formats, but the
+    resulting colors may be unexpected due to the mismatch in color formats.
+
+Constants
+---------
+
+.. data:: framebuf.MVLSB
+
+    Monochrome (1-bit) color format
+
+.. data:: framebuf.RGB565
+
+    Red Green Blue (16-bit, 5+6+5) color format
+
+.. data:: framebuf.GS4_HMSB
+
+    Grayscale (4-bit) color format

docs/library/index.rst

@@ -153,6 +153,7 @@ the following libraries.
 .. toctree::
    :maxdepth: 1
 
+   framebuf.rst
    machine.rst
    micropython.rst
    network.rst