qbzf

quadratic bezier font format designed to render in a fragment shader

status: somewhat usable but many numeric stability issues

This package comes with 3 sections: a javascript library, glsl shader code, and a command-line tool.

Use the command-line tool to generate font data from a ttf file to pass into the javascript api.

The javascript api generates textures that can be read by the shader code.

example

To run this example: budo ok.js -- -t glslify

var glsl = require('glslify')
var regl = require('regl')()
var QBZF = require('qbzf')

var draw = null
window.addEventListener('resize', frame)

var data = { curves: null, grid: null }
fromData(Uint8Array.from([ // hard-coded data for o and k glyphs
  113,98,122,102,49,10,128,16,24,107,196,18,244,2,244,2,0,184,18,168,24,220,8,0,
  2,168,24,216,8,0,2,173,14,224,25,198,7,132,11,0,233,27,151,8,132,29,167,9,157,
  11,0,211,26,198,8,2,197,8,211,8,0,52,111,202,19,226,1,226,1,57,234,17,246,17,
  178,29,190,15,2,0,243,6,0,211,3,231,1,255,3,229,1,171,1,247,4,2,0,4,145,3,170,
  1,249,4,136,4,229,1,214,3,229,1,2,0,246,6,0,210,3,232,1,136,4,232,1,172,1,248,
  4,2,0,4,142,3,171,1,246,4,255,3,234,1,209,3,234,1,0,184,2,2,0,164,11,0,242,5,
  183,2,186,6,183,2,146,2,223,6,2,0,4,165,4,145,2,223,6,177,6,183,2,241,5,183,2,
  2,0,161,11,0,243,5,184,2,171,6,186,2,143,2,224,6,2,0,4,168,4,144,2,224,6,186,
  6,184,2,244,5,184,2
]))
// or load from a file:
// fetch('djvsans').then(r => r.arrayBuffer()).then(r => fromData(new Uint8Array(r)))

function fromData(buf) {
  var qbzf = new QBZF(buf)
  data.curves = qbzf.curves
  data.curves.texture = regl.texture(data.curves)
  data.grid = qbzf.write({
    text: 'ok',
    strokeWidth: 10, // in units
  })
  data.grid.texture = regl.texture(data.grid)
  draw = build(data.grid.n)
  frame()
}

function frame() {
  regl.poll()
  regl.clear({ color: [0,0,0,1], depth: true })
  if (data) draw(data)
}

function build(n) {
  return regl({
    frag: glsl`
      precision highp float;
      #pragma glslify: QBZF = require('qbzf/h')
      #pragma glslify: create_qbzf = require('qbzf/create')
      #pragma glslify: read_curve = require('qbzf/read')

      varying vec2 vpos;
      uniform sampler2D curveTex, gridTex;
      uniform vec2 curveSize, gridUnits, gridSize, gridDim;
      uniform float gridN, strokeWidth;

      void main() {
        vec2 uv = vpos*0.5+0.5;
        QBZF qbzf = create_qbzf(
          uv, gridN, gridSize, gridUnits, gridDim,
          gridTex, curveSize
        );
        float ldist = 1e30;
        for (int i = 0; i < ${n}; i++) {
          vec4 curve = read_curve(qbzf, gridTex, curveTex, float(i));
          if (curve.x < 0.5) break;
          qbzf.count += curve.y;
          ldist = min(ldist,length(curve.zw));
        }
        float a = 5.0; // aliasing width in font units
        float outline = 1.0-smoothstep(strokeWidth-a,strokeWidth+a,ldist);

        vec3 fill = vec3(0,0,0);
        vec3 stroke = vec3(1,1,1);
        vec3 bg = vec3(0.5,0,1);

        vec3 c = mix(
          mix(bg,stroke,outline),
          mix(stroke,fill,smoothstep(ldist,0.0,a)),
          mod(qbzf.count,2.0)
        );
        gl_FragColor = vec4(c,1);
      }
    `,
    vert: `
      precision highp float;
      attribute vec2 position;
      varying vec2 vpos;
      void main() {
        vpos = position;
        gl_Position = vec4(position,0,1);
      }
    `,
    uniforms: {
      curveTex: regl.prop('curves.texture'),
      curveSize: regl.prop('curves.size'),
      gridTex: regl.prop('grid.texture'),
      gridUnits: regl.prop('grid.units'),
      gridSize: regl.prop('grid.grid'),
      gridDim: regl.prop('grid.dimension'),
      gridN: n,
      strokeWidth: regl.prop('grid.strokeWidth'),
    },
    attributes: { position: [-4,-4,-4,+4,+4,+0] },
    elements: [0,1,2],
  })
}

api

var QBZF = require('qbzf')
var Atlas = require('qbzf/atlas')

#pragma glslify: QBZF = require('qbzf/qbzf.h')
#pragma glslify: create_qbzf = require('qbzf/create')
#pragma glslify: read_curve = require('qbzf/read')

var qbzf = QBZF(fontSrc, opts)

Create a new qbzf instance from a Uint8Array of fontSrc (created by the qbzf command) and:

• opts.density - default [200,200]
• opts.epsilon - default 1e-8

qbzf.curves

Curve texture data with:

• qbzf.curves.data - Uint8Array of curve texture data
• qbzf.curves.width - width in pixels of the curve texture
• qbzf.curves.height - height in pixels of the curve texture
• qbzf.curves.size - 2-element array of [width,height]

qbzf.unitsPerEm

Font unit measurement from the original font file.

qbzf.measure(opts)

Return only the calculated units, grid, offset and bbox without writing to a grid texture.

var grid = qbzf.write(opts)

Create a grid texture from opts:

• opts.text - string to stamp glyphs into output grid texture
• opts.offset - [x,y] translation in units
• opts.padding - padding in units as [left,bottom,right,top]
• opts.strokeWidth - width of stroke in units. default 0
• opts.data - Uint8Array to write data into. created if not provided.

The resulting grid object has:

• grid.data - uint8array of grid texture data to read from
• grid.width - width of grid texture in pixels
• grid.height - height of grid texture in pixels
• grid.dimension - 2-element array of [grid.width,grid.height]
• grid.units - size of font data in font units
• grid.grid - dimensions of logical grid
• grid.n - number of curves stored in each cell

var atlas = Atlas(qbzf, opts)

Create an atlas to manage multiple labels at once using one texture per each n and so one draw call per n along with corresponding label geometry.

• opts.attributes - array of strings to set additional attributes in atlas.add() which will also appear alongside other records in atlas.build()

var id = atlas.add(opts)

Add a text label with all the arguments to qbzf.write() plus:

• opts.height - height of 1 em in output coordinate scale
• opts.location - translation in output coordinate scale (default: [0,0])
• opts.id - set the id directly. must be unique

Returns the id provided or an assigned unique id if none was provided.

atlas.remove(id)

Remove a label by its id.

atlas.clear()

Remove all labels.

var data = atlas.build()

data is an object mapping n keys to a grid g with:

• g.curves - reference to qbzf.curves
• g.positions - vec2 attribute for coordinates in output coordinate scale
• g.uv - vec2 attribute for each label's coordinates (0 to 1 in x and y)
• g.cells - element indexes for triangle geometry
• g.offsets - float attribute for pixel offset
• g.units - vec2 attribute for size of label in font units
• g.size - vec2 attribute for grid dimensions in number of cells
• g.id - id assigned to label (float unless set to something else)

These are merged with everything set in opts.attributes.

QBZF qbzf = create(vec2 uv, float n, vec2 size, vec2 units, vec3 dim, sampler2D grid_tex, vec2 curve_size)

Create a glsl QBZF struct from the given parameters:

• vec2 uv - texture coordinates for lookup (0 to 1 in each dimension)
• float n - number of curves per cell
• vec2 size - dimensions of logical grid
• vec3 dim - dimensions of grid in pixels and pixel offset to start reading
• sampler2D grid_tex - grid texture data
• vec2 curve_size - dimensions of curve texture in pixels

The qbzf.count is initialized with the number of crossings for the right support for the given uv (either 0 or 1).

QBZF qbzf = create(vec2 uv, float n, vec2 size, vec2 units, vec2 dim, sampler2D grid_tex, vec2 curve_size)

Alias for create(uv, n, size, units, vec3(dim,0), grid_tex, curve_size).

This sets the offset to 0.

vec4 curve = read_curve(QBZF qbzf, sampler2D grid_tex, sampler2D curve_tex, float i)

Read curve i referenced the current cell in grid_tex with a lookup into curve_tex and calculate:

• curve.x - index of the curve plus one. 0.0 if there is no curve for this index.
• curve.y - number of raycast crossings
• curve.z - distance from the current point to the curve in x component
• curve.w - distance from the current point to the curve in y component

Sum every curve.y with qbzf.count to get the total number of crossings.

If the number of corssings is even, you're outside the polygon and if odd you're inside.

usage

usage: qbzf (INFILE)

  -i INFILE     Read from this font file.
  -o OUTFILE    Write bezier text output to this file. Default: "-" (stdout)

  -l --list     List all codes from the input ttf font file.
  -m --meta     List unitsPerEm and glyph unicodes as ranges for each INFILE,
                which can be a ttf or qbzf font file.

  -u --unicode  Only include glyphs with these unicode values.
  -c --char     Only include glyphs with these character values.
  -x --index    Only include glyphs with these indexes.

  -h --help     Show this message.
  -v --version  Print software version (1.1.0).

  Unicode and index lists can be specified with multiple flags (-u 97 -u 98 -u 99)
  or with comma-separated lists (-u 97,98,99).

  Char lists can be specified with multiple flags or comma-separated lists.
  For a literal comma, use "-c,".

  Unicodes can be specified in hexadecimal with a leading "u": (-u u0061).

install

For the qbzf command:

npm install -g qbzf

For the library:

npm install qbzf

license

bsd