# `framebuf` — 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 framebuf.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.

FrameBuffer.fill(c)

  Fill the entire FrameBuffer with the specified color.

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.

FrameBuffer.hline(x, y, w, c)

FrameBuffer.vline(x, y, h, c)

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.

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.

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.

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 `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

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

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.

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

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.

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.

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.

framebuf.RGB565

  Red Green Blue (16-bit, 5+6+5) color format

framebuf.GS2_HMSB

  Grayscale (2-bit) color format

framebuf.GS4_HMSB

  Grayscale (4-bit) color format

framebuf.GS8

  Grayscale (8-bit) color format

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External links
  openmv.io
  forums.openmv.io
  github.com/openmv/openmv
  micropython.org
  forum.micropython.org
  github.com/micropython/micropython