framebuf — Frame buffer manipulation

Warning

Though this MicroPython-based library may be available for use in some builds of CircuitPython, it is unsupported and its functionality may change in the future, perhaps significantly. As CircuitPython continues to develop, it may be changed to comply more closely with the corresponding standard Python library. You will likely need to change your code later if you rely on any non-standard functionality it currently provides.

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 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)
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

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])

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 instances utilising different formats, but the resulting colors may be unexpected due to the mismatch in color formats.

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 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.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 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.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