Flat — Generative infrastructure for Python

Flat is a library for creating and manipulating digital forms of fine arts. Its aim is to enable experimentation with and testing of unpredictable or automated processes, to inspect the beginning of the "new".

It grew out of the needs for generative design, architecture and art. The concept of "design" is more of a subject of study yet to be delved into, hence the fitter term for subtitle is "infrastructure".

It is written in pure Python and distributed under a liberal license.

Content

• Features
• Core concepts
• Tutorial
• API reference
• Installation
• Source code
• Previous releases
• Contact

Features

• Graphic formats
  • PNG, JPEG, PDF, SVG, OpenType (both TrueType and PostScript outlines), STL
• Color spaces
  • grayscale, grayscale + alpha, RGB, RGBA, CMYK, spot colors, overprint
• Image manipulation
  • resizing, blurring, dithering, ...
• Image synthesis
  • Bezier path rasterization, BVH accelerated path tracing with explicit emitters and stratified sampling
• Vector graphic primitives
  • line, polyline, ..., path, text, outlines, groups and units
• Typography
  • kerning, greedy line breaking, threaded text frames
• Computational geometry
  • Boolean operation on polygons
• Data visualization
  • tree layout

Core concepts

Flat library consists of three (slightly overlapping) parts: image, document and scene. An image is basically a container of pixels and a color kind. There are a few methods which operate over those pixels, such as "blur" or "put". It is possible to create completely new image, by opening a file or by "rasterizing" a page of document.

Document is then assembled from pages, and each page holds number of "placed" items, both of which can be exported, too. Here it also makes sense to introduce other entities: colors, shapes and strikes. There is support for following colors or color spaces, if you will: the usual ones (grayscale, RGB, CMYK, ...), spot colors that can be used for controlling the application of special colorants and "overprint", which allows for printing of a graphic figure without erasing anything below it. A shape includes both graphical properties such as stroke width or miter limit and means of creating items with said properties that are to be "placed" into a page, for example "line" or "circle". Strike is a similar combination of text attributes (font, size, color, ...) and a way of constructing text "spans". A span likewise connects text string to text attributes, one or more spans can form a "paragraph", which in turn may form "text" or "outlines". Outlines are similar to texts but they use paths of glyph outlines, instead of characters. One additional thing to note is that placed texts or outlines may be linked into a story or "chain" of blocks, making the text gradually "flow" from one text frame to another. Any of the items may be placed into a "group" as well.

Finally, a scene is made of (possibly light emitting) materials, meshes built of triangular faces defined by "triplets" of 3D vertices and a camera.

Tutorial

from flat import rgb, font, shape, strike, document

red = rgb(255, 0, 0)
lato = font.open('Lato-Reg.otf')
figure = shape().stroke(red).width(2.5)
headline = strike(lato).color(red).size(20, 24)

d = document(100, 100, 'mm')
p = d.addpage()
p.place(figure.circle(50, 50, 20))
p.place(headline.text('Hello world!')).frame(10, 10, 80, 80)
p.image(kind='rgb').png('hello.png')
p.svg('hello.svg')
d.pdf('hello.pdf')

Short commentary:

We first prepared some invariants which we are going to use later, like the body typeface, some RGB color or a typeface we opened from a font file. One can think of shape and strike as of customizable factories which produce more concrete objects, for example lines or spans of text.

Next is the basic document hierarchy with just one page that can have items be placed into. The origin of coordinate system (0, 0) is at the top left corner and most of the time the default unit is "points" (1 inch = 72 points). A placed item may have some additional properties as position or frame. The latter is used to define the boundaries inside whose the text may run. As Flat currently lacks any kind of color management, we need to use the same color space for rasterizing the page into a PNG file. To access a page at any time one can simply keep a reference to it (p). Lastly, note that PDF is one of the few graphic formats which can hold multiple pages.

API reference

image.py

• image.open(path)
  • • Open an image located at path. Supported formats are JPEG and PNG.
• image(width, height, kind='rgb')
  • • Create an image width by height pixels in resolution, where kind can be one of: 'g' (grayscale), 'ga' (grayscale + alpha), 'rgb', 'rgba', 'cmyk'.
  • copy()
    • Return a deep copy of the image.
  • get(x, y)
    • Return the color values of pixel at x, y.
  • put(x, y, components)
    • Set the color of pixel at x, y to components.
  • fill(components)
    • Fill the image with solid color of components.
  • white()
    • Fill the image with solid white.
  • black()
    • Fill the image with solid black.
  • blit(x, y, source)
    • Copy a region from source. Position of the region is x, y in this image, 0, 0 in the source. Size of the region is the size of the source, cropping it to size of this image as necessary.
  • crop(x, y, width, height)
    • Crop the image to frame with origin at x, y and size width, height. The result will not enlarge beyond original size.
  • flip(horizontal, vertical)
    • Flip the image horizontally and/or vertically.
  • transpose()
    • Flip the image over the diagonal.
  • rotate(clockwise)
    • Rotate the image by 90 degrees clockwise if clockwise is True, anti-clockwise otherwise.
  • resize(width=0, height=0, interpolation='bicubic')
    • Resize the image to width by height, where interpolation can be one of: 'nearest', 'bicubic', 'lanczos'. Nearest-neighbor is fastest kernel and produces "pixelated" look when upsizing, bicubic is good general-purpose filter, Lanczos resampling preserves most detail and is slowest of the three. 0 width or height maintains the aspect ratio.
  • rescale(factor, interpolation='bicubic')
    • Similar to resize but uses scale factor to calculate new dimensions.
  • blur(radius)
    • Blur the image with Gaussian filter kernel.
  • dither(levels=2)
    • Reduce the number of grayscale intensities to levels using Burkes dithering.
  • gamma(value)
    • Perform gamma correction of value on the image.
  • invert()
    • Invert color of the image.
  • png(path='', optimized=False)
    • Return the image serialized into PNG format. If path is set, save it as well. Improve the compression by setting optimized to True.
  • jpeg(path='', quality=95)
    • Return the image serialized into JPEG format. If path is set, save it as well. Higher (up to 100) quality lowers the perceptible loss in image quality but increases the storage size.
• placedimage
  • • Don't call directly. Use page.place() instead.
  • position(x, y)
    • Move the placed image to x, y.
  • frame(x, y, width, height)
    • Move the placed image to x, y and resize it to width, height.
  • fitwidth(width)
    • Proportionally scale the placed image to match width.
  • fitheight(height)
    • Proportionally scale the placed image to match height.
• raw(width, height)
  • • Create a so called "raw" RGB image that comprises of floating-point intensities.
  • put(x, y, r, g, b)
    • Set the color of pixel at x, y to r, g, b.
  • tonemapped(key=0.18, white=1.0)
    • Return an image with reduced dynamic range of integer values 0-255, where key indicates whether the scene is subjectively light or dark, typically varying from 0.18 to 0.4, and white is the smallest luminance mapped to pure white.

document.py

• page
  • • Don't call directly. Use document.addpage() instead.
  • meta(title)
    • Set metadata about the page, such as title.
  • size(width, height, units='mm')
    • Set the default document size to width by height, where units can be one of: 'pt', 'mm', 'cm', 'in'.
  • place(item)
    • Place an item on the page.
  • chain(block)
    • Add new text block to the block, enabling its text to flow along the linked blocks. A chain eventually eliminates overflow.
  • svg(path='', compress=False)
    • Return the page serialized into SVG format. If path is set, save it as well. Reduce size by setting compress to True (currently not implemented).
  • image(ppi=72, kind='g')
    • Return the page rasterized at ppi (pixels per inch) into image of kind.
• document.open(path)
  • • Open a document located at path. Currently not implemented.
• document(width=210.0, height=297.0, units='mm')
  • • Create a document with dimensions of width by heightunits.
  • meta(title)
    • Set metadata about the document, such as title.
  • size(width, height, units='mm')
    • Set dimensions of the document to width by heightunits.
  • addpage()
    • Create and add one page to the document and return it.
  • pdf(path='', compress=False)
    • Return the document serialized into PDF. If path is set, save it as well. Reduce size by setting compress to True (currently not implemented).

mesh.py

• mesh.openstl(path)
  • • Open an STL mesh located at path.
• mesh(triplets)
  • • Create a mesh with triplets of triangular face vertices. Each vertex is a triplet of x, y, z coordinates.
  • stl(path='')
    • Return the mesh serialized into STL format. If path is set, save it as well.

scene.py

• diffuse(reflectance, emittance=None)
  • • Create a diffuse material with reflectance and emittance, each of being an RGB floating-point triplet.
• scene()
  • • Create empty scene.
  • environment(sky, ground)
    • Set the sky and ground emittance, each of being an RGB floating-point triplet.
  • camera(origin, target, length=50.0)
    • Point the camera from origin to target, each of being an 3D point coordinate. Set focal length to length in millimetres.
  • clear()
    • Remove all items from the scene.
  • add(mesh, material)
    • Add mesh combined with material to the scene.
  • render(width, height, samples=10, multiprocessing=True, info=True)
    • Render the scene to raw image with size width by height pixels using samples × samples number of path tracing samples. To use all available cores set multiprocessing to True and to report rendering progress set info to True.

color.py

• gray(intensity)
  • • Create a grayscale color with intensity. 0 corresponds to black, 255 to white.
• ga(g, a)
  • • Create a grayscale color with intensity g and alpha a. 0 corresponds to black/transparent, 255 to white/opaque.
• rgb(r, g, b)
  • • Create an RGB color with intensities r, g, b. 0 corresponds to absence of component, 255 to maximum intensity.
• rgba(r, g, b, a)
  • • Create an RGBA color with intensities r, g, b and alpha a. 0 corresponds to absence of component/coverage, 255 to maximum intensity/opacity.
• cmyk(c, m, y, k)
  • • Create a CMYK color with tints c, m, y, k. 0 denotes the absence of colorant, 100 means maximum concentration.
• spot(name, fallback)
  • • Create a spot color with name and CMYK fallback used in case of absence of colorant in output device.
  • thinned(tint)
    • Duplicate the color and sets the amount of application of its colorant to tint. 0 denotes the absence of colorant, 100 means maximum concentration.
• overprint(color)
  • • Create a wrapper of color which enables overprinting. Argument may be one of: cmyk, spot or devicen. When printing without overprint a graphic figure erases everything beneath it. With overprint it is possible to stack a layer of paint over preceding layers.

font.py

• font.open(path, index=0)
  • • Open a font file located at path.
• font
  • • Don't call directly, for now. Use font.open() instead.

shape.py

• shape()
  • • Create an abstract shape. Defaults are: gray(0) stroke, no fill, 'butt' cap, 'miter' join and 4.0 miter limit.
  • stroke(color)
    • Set the stroke color to color.
  • fill(color)
    • Set the fill color to color.
  • nostroke()
    • Disable stroke color.
  • nofill()
    • Disable fill color.
  • width(value, units='pt')
    • Set the stroke width to value, in units.
  • cap(kind)
    • Set the stroke cap to kind, may be one of: 'butt', 'round', 'square'.
  • join(kind)
    • Set the stroke join to kind, may be one of: 'miter', 'round', 'bevel'.
  • limit(value)
    • Set the miter limit.
  • line(x0, y0, x1, y1)
    • Create a line from x0, y0 to x1, y1.
  • polyline(*coordinates)
    • Create an open polyline with a sequence of altering x and y coordinates.
  • polygon(*coordinates)
    • Create closed polygon with a sequence of altering x and y coordinates.
  • rectangle(x, y, width, height)
    • Create a rectangle with origin x, y and size width, height.
  • circle(x, y, r)
    • Create a circle with center at x, y and radius r.
  • ellipse(x, y, rx, ry)
    • Create an ellipse with center at x, y and horizontal/vertical radius rx/ry.
  • path(*commands)
    • Create a path constructed out of commands. Valid types are: moveto, lineto, quato, curveto, closepath.
• placedshape
  • • Don't call directly. Use page.place() instead.
  • position(x, y)
    • Move the placed shape to x, y.

command.py

• moveto(x, y)
  • • Create a command which moves current point to x, y.
• lineto(x, y)
  • • Create a command which draw a line from current point to x, y.
• quadto(x1, y1, x, y)
  • • Create a command which draw a quadratic Bezier curve from current point to x, y, using control point x1, y1.
• curveto(x1, y1, x2, y2, x, y)
  • • Create a command which draw a cubic Bezier curve from current point to x, y, using control point x1, y1 and x2, y2.
• closepath
  • • Singleton command which closes the current subpath.
• moveto, lineto, quadto, curveto, closepath
  • transform(a, b, c, d, e, f)
    • Transform the command by matrix a, b, c, d, e, f.

svg.py

• parsepath(data)
  • • Parse SVG Path data into sequence of path commands.

path.py

• union(subject, clipper, perturbation=0.0)
• intersection(subject, clipper, perturbation=0.0)
• difference(subject, clipper, perturbation=0.0)
  • • Return a sequence of path commands resulting from given Boolean opeation on subject and clipper polygons. Scatter the vertices by ± perturbation amount.

text.py

• strike(font)
  • • Create a strike with font. Defaults are: 10 pt size, 12 pt leading and gray(0) color.
  • size(size, leading=0.0, units='pt')
    • Set the text size and line spacing to size and leading, in units. Zero leading calculates a default value according to size.
  • color(color)
    • Set the text color to color.
  • width(string)
    • Measure the width of string, in points.
  • span(string)
    • Create a text span by combining the strike and string. Spans may form a paragraph.
  • paragraph(string)
    • Create a text paragraph with one span by combining the strike and string. Paragraphs may form a text.
  • text(string)
    • Create a text by breaking string to paragraphs at newline characters, with each paragraph having one span. Placed texts may be chained to enable text flow. Text yields a sequence of characters tied to the font.
  • outlines(string)
    • Create outlines by breaking string to paragraphs at newline characters, with each paragraph having one span. Placed outlines may be chained to enable text flow. Outlines yield a sequence of Bezier paths based on glyph outlines.
• paragraph(spans)
  • • Create a paragraph containing spans.
• text.open(path, substitutes), outlines.open(path, substitutes)
  • • Open a text file located at path and use font substitutes. Currently not implemented.
• text(paragraphs), outlines(*paragraphs)
  • • Create a text/outlines containing paragraphs.
• placedtext, placedoutlines
  • • Don't call directly. Use page.place() instead. Blocks have infinite sizes by default.
  • position(x, y)
    • Move the placed text to x, y.
  • frame(x, y, width, height)
    • Move the placed text to x, y, resize it to width, height and reflow it along the chain.
  • overflow()
    • Return whether the placed text flows over the frame(s).
  • lines()
    • Return the text content broken into lines according to current layout.

group.py

• group.open(path)
  • • Open a vector graphics file located at path. Currently not implemented.
• group(units='mm')
  • • Create a group with dimensions in units.
  • units(units='mm')
    • Set the units of the group.
  • place(item)
    • Place an item into the group.
  • chain(block)
    • Add new text block to the block, enabling its text to flow along the linked blocks. A chain eventually eliminates overflow.
• placedgroup
  • • Don't call directly. Use page.place() instead.
  • position(x, y)
    • Move the placed group to x, y.
  • scale(factor)
    • Scale the placed group by factor.

extra.py

• tree(item)
  • • Create a tree rooted at item.
  • add(item)
    • Add a child (i.e. another tree) with item and return it.
  • layout()
    • Use horizontal layout to position the nodes.
  • transpose()
    • Flip between horizontal and vertical layout.
  • frame(x, y, width, height)
    • Move the tree to x, y and resize it to width, height.
  • nodes()
    • Return all the tree nodes in depth-first order. Each node has x, y coordinates, parent, children and the original item.

even.py

• view(data)
  • • Load data into the viewer if called inside of Even, otherwise do nothing.

Installation

pip install flat

It currently requires Python 2.7.

Alternatively, there is Even application which integrates the library, a viewer and Python editor.

Source code

github.com/xxyxyz/flat

pypi.python.org/pypi/flat

Contact

Juraj Sukop, contact@xxyxyz.org