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