169 lines
6.2 KiB
ReStructuredText
169 lines
6.2 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 = framebuf.FrameBuffer(bytearray(100 * 10 * 2), 100, 10, 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, 9, 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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permissible values are listed under Constants below. These set the
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number of bits used to encode a color value and the layout of these
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bits in *buffer*.
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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=-1, palette=None)
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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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The *palette* argument enables blitting between FrameBuffers with differing
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formats. Typical usage is to render a monochrome or grayscale glyph/icon to
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a color display. The *palette* is a FrameBuffer instance whose format is
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that of the current FrameBuffer. The *palette* height is one pixel and its
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pixel width is the number of colors in the source FrameBuffer. The *palette*
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for an N-bit source needs 2**N pixels; the *palette* for a monochrome source
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would have 2 pixels representing background and foreground colors. The
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application assigns a color to each pixel in the *palette*. The color of the
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current pixel will be that of that *palette* pixel whose x position is the
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color of the corresponding source pixel.
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Constants
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---------
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.. data:: framebuf.MONO_VLSB
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Monochrome (1-bit) color format
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This defines a mapping where the bits in a byte are vertically mapped with
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bit 0 being nearest the top of the screen. Consequently each byte occupies
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8 vertical pixels. Subsequent bytes appear at successive horizontal
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locations until the rightmost edge is reached. Further bytes are rendered
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at locations starting at the leftmost edge, 8 pixels lower.
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.. data:: framebuf.MONO_HLSB
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Monochrome (1-bit) color format
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This defines a mapping where the bits in a byte are horizontally mapped.
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Each byte occupies 8 horizontal pixels with bit 7 being the leftmost.
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Subsequent bytes appear at successive horizontal locations until the
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rightmost edge is reached. Further bytes are rendered on the next row, one
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pixel lower.
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.. data:: framebuf.MONO_HMSB
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Monochrome (1-bit) color format
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This defines a mapping where the bits in a byte are horizontally mapped.
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Each byte occupies 8 horizontal pixels with bit 0 being the leftmost.
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Subsequent bytes appear at successive horizontal locations until the
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rightmost edge is reached. Further bytes are rendered on the next row, one
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pixel lower.
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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.GS2_HMSB
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Grayscale (2-bit) color format
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.. data:: framebuf.GS4_HMSB
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Grayscale (4-bit) color format
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.. data:: framebuf.GS8
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Grayscale (8-bit) color format
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