freetype

README

The Freetype font rasterizer in the Go programming language.

To download and install from source:
$ go get github.com/tdewolff/freetype

It is an incomplete port:
  * It only supports TrueType fonts, and not Type 1 fonts nor bitmap fonts.
  * It only supports the Unicode encoding.

There are also some implementation differences:
  * It uses a 26.6 fixed point co-ordinate system everywhere internally,
    as opposed to the original Freetype's mix of 26.6 (or 10.6 for 16-bit
    systems) in some places, and 24.8 in the "smooth" rasterizer.

Freetype-Go is derived from Freetype, which is written in C. Freetype is
copyright 1996-2010 David Turner, Robert Wilhelm, and Werner Lemberg.
Freetype-Go is copyright The Freetype-Go Authors, who are listed in the
AUTHORS file.

Unless otherwise noted, the Freetype-Go source files are distributed
under the BSD-style license found in the LICENSE file.

Documentation

Overview

The freetype package provides a convenient API to draw text onto an image. Use the freetype/raster and freetype/truetype packages for lower level control over rasterization and TrueType parsing.

Index

• func ParseFont(b []byte) (*truetype.Font, error)
• func Pt(x, y int) fixed.Point26_6
• type Context
  • func NewContext() *Context
  • func (c *Context) DrawString(s string, p fixed.Point26_6) (fixed.Point26_6, error)
  • func (c *Context) PointToFixed(x float64) fixed.Int26_6
  • func (c *Context) SetClip(clip image.Rectangle)
  • func (c *Context) SetDPI(dpi float64)
  • func (c *Context) SetDst(dst draw.Image)
  • func (c *Context) SetFont(f *truetype.Font)
  • func (c *Context) SetFontSize(fontSize float64)
  • func (c *Context) SetHinting(hinting font.Hinting)
  • func (c *Context) SetSrc(src image.Image)

Functions

func ParseFont

func ParseFont(b []byte) (*truetype.Font, error)

ParseFont just calls the Parse function from the freetype/truetype package. It is provided here so that code that imports this package doesn't need to also include the freetype/truetype package.

func Pt

func Pt(x, y int) fixed.Point26_6

Pt converts from a co-ordinate pair measured in pixels to a fixed.Point26_6 co-ordinate pair measured in fixed.Int26_6 units.

Types

type Context

type Context struct {
	// contains filtered or unexported fields
}

A Context holds the state for drawing text in a given font and size.

func NewContext

func NewContext() *Context

NewContext creates a new Context.

func (*Context) DrawString

func (c *Context) DrawString(s string, p fixed.Point26_6) (fixed.Point26_6, error)

DrawString draws s at p and returns p advanced by the text extent. The text is placed so that the left edge of the em square of the first character of s and the baseline intersect at p. The majority of the affected pixels will be above and to the right of the point, but some may be below or to the left. For example, drawing a string that starts with a 'J' in an italic font may affect pixels below and left of the point.

p is a fixed.Point26_6 and can therefore represent sub-pixel positions.

func (*Context) PointToFixed

func (c *Context) PointToFixed(x float64) fixed.Int26_6

PointToFixed converts the given number of points (as in "a 12 point font") into a 26.6 fixed point number of pixels.

func (*Context) SetClip

func (c *Context) SetClip(clip image.Rectangle)

SetClip sets the clip rectangle for drawing.

func (*Context) SetDPI

func (c *Context) SetDPI(dpi float64)

SetDPI sets the screen resolution in dots per inch.

func (*Context) SetDst

func (c *Context) SetDst(dst draw.Image)

SetDst sets the destination image for draw operations.

func (*Context) SetFont

func (c *Context) SetFont(f *truetype.Font)

SetFont sets the font used to draw text.

func (*Context) SetFontSize

func (c *Context) SetFontSize(fontSize float64)

SetFontSize sets the font size in points (as in "a 12 point font").

func (*Context) SetHinting

func (c *Context) SetHinting(hinting font.Hinting)

SetHinting sets the hinting policy.

func (*Context) SetSrc

func (c *Context) SetSrc(src image.Image)

SetSrc sets the source image for draw operations. This is typically an image.Uniform.