matplotlib.backends.backend_cairo

A Cairo backend for matplotlib

Author:Steve Chaplin and others

This backend depends on cairo, and either on cairocffi, or (Python 2 only) on pycairo.

class matplotlib.backends.backend_cairo.ArrayWrapper(myarray)

Bases: object

Thin wrapper around numpy ndarray to expose the interface expected by cairocffi. Basically replicates the array.array interface.

buffer_info()

matplotlib.backends.backend_cairo.FigureCanvas

alias of matplotlib.backends.backend_cairo.FigureCanvasCairo

class matplotlib.backends.backend_cairo.FigureCanvasCairo(figure)

Bases: matplotlib.backend_bases.FigureCanvasBase

print_pdf(fobj, *args, **kwargs)

print_png(fobj, *args, **kwargs)

print_ps(fobj, *args, **kwargs)

print_svg(fobj, *args, **kwargs)

print_svgz(fobj, *args, **kwargs)

supports_blit = False

class matplotlib.backends.backend_cairo.GraphicsContextCairo(renderer)

Bases: matplotlib.backend_bases.GraphicsContextBase

get_rgb()

returns a tuple of three or four floats from 0-1.

restore()

Restore the graphics context from the stack - needed only for backends that save graphics contexts on a stack

set_alpha(alpha)

Set the alpha value used for blending - not supported on all backends. If alpha=None (the default), the alpha components of the foreground and fill colors will be used to set their respective transparencies (where applicable); otherwise, alpha will override them.

set_capstyle(cs)

Set the capstyle as a string in ('butt', 'round', 'projecting')

set_clip_path(path)

Set the clip path and transformation. Path should be a TransformedPath instance.

set_clip_rectangle(rectangle)

Set the clip rectangle with sequence (left, bottom, width, height)

set_dashes(offset, dashes)

Set the dash style for the gc.

Parameters:

dash_offset : float

is the offset (usually 0).

dash_list : array_like

specifies the on-off sequence as points. (None, None) specifies a solid line

set_foreground(fg, isRGBA=None)

Set the foreground color. fg can be a MATLAB format string, a html hex color string, an rgb or rgba unit tuple, or a float between 0 and 1. In the latter case, grayscale is used.

If you know fg is rgba, set isRGBA=True for efficiency.

set_joinstyle(js)

Set the join style to be one of ('miter', 'round', 'bevel')

set_linewidth(w)

Set the linewidth in points

class matplotlib.backends.backend_cairo.RendererCairo(dpi)

Bases: matplotlib.backend_bases.RendererBase

static convert_path(ctx, path, transform, clip=None)

draw_image(gc, x, y, im)

Draw an RGBA image.

Parameters:

gc : GraphicsContextBase

a graphics context with clipping information.

x : scalar

the distance in physical units (i.e., dots or pixels) from the left hand side of the canvas.

y : scalar

the distance in physical units (i.e., dots or pixels) from the bottom side of the canvas.

im : array_like, shape=(N, M, 4), dtype=np.uint8

An array of RGBA pixels.

transform : matplotlib.transforms.Affine2DBase

If and only if the concrete backend is written such that option_scale_image() returns True, an affine transformation may be passed to draw_image(). It takes the form of a Affine2DBase instance. The translation vector of the transformation is given in physical units (i.e., dots or pixels). Note that the transformation does not override x and y, and has to be applied before translating the result by x and y (this can be accomplished by adding x and y to the translation vector defined by transform).

draw_markers(gc, marker_path, marker_trans, path, transform, rgbFace=None)

Draws a marker at each of the vertices in path. This includes all vertices, including control points on curves. To avoid that behavior, those vertices should be removed before calling this function.

This provides a fallback implementation of draw_markers that makes multiple calls to draw_path(). Some backends may want to override this method in order to draw the marker only once and reuse it multiple times.

Parameters:

gc : GraphicsContextBase

The graphics context

marker_trans : matplotlib.transforms.Transform

An affine transform applied to the marker.

trans : matplotlib.transforms.Transform

An affine transform applied to the path.

draw_path(gc, path, transform, rgbFace=None)

Draws a Path instance using the given affine transform.

draw_text(gc, x, y, s, prop, angle, ismath=False, mtext=None)

Draw the text instance

Parameters:

gc : GraphicsContextBase

the graphics context

x : scalar

the x location of the text in display coords

y : scalar

the y location of the text baseline in display coords

s : str

the text string

prop : matplotlib.font_manager.FontProperties

font properties

angle : scalar

the rotation angle in degrees

mtext : matplotlib.text.Text

the original text object to be rendered

Notes

backend implementers note

When you are trying to determine if you have gotten your bounding box right (which is what enables the text layout/alignment to work properly), it helps to change the line in text.py:

if 0: bbox_artist(self, renderer)

to if 1, and then the actual bounding box will be plotted along with your text.

fontangles = {'italic': <MyCairoCffi name='mock.FONT_SLANT_ITALIC' id='140677916054864'>, 'normal': <MyCairoCffi name='mock.FONT_SLANT_NORMAL' id='140677916063280'>, 'oblique': <MyCairoCffi name='mock.FONT_SLANT_OBLIQUE' id='140677916075792'>}

fontweights = {100: <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 200: <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 300: <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 400: <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 500: <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 600: <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 700: <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 800: <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 900: <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 'ultralight': <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 'light': <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 'normal': <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 'medium': <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 'regular': <MyCairoCffi name='mock.FONT_WEIGHT_NORMAL' id='140677916025744'>, 'semibold': <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 'bold': <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 'heavy': <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 'ultrabold': <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>, 'black': <MyCairoCffi name='mock.FONT_WEIGHT_BOLD' id='140677916038256'>}

get_canvas_width_height()

return the canvas width and height in display coords

get_text_width_height_descent(s, prop, ismath)

Get the width, height, and descent (offset from the bottom to the baseline), in display coords, of the string s with FontProperties prop

new_gc()

Return an instance of a GraphicsContextBase

points_to_pixels(points)

Convert points to display units

You need to override this function (unless your backend doesn't have a dpi, e.g., postscript or svg). Some imaging systems assume some value for pixels per inch:

points to pixels = points * pixels_per_inch/72.0 * dpi/72.0

Parameters:

points : scalar or array_like

a float or a numpy array of float

Returns:

Points converted to pixels

set_ctx_from_surface(surface)

set_width_height(width, height)