bitmapfont

README

bitmapfont rendering for OpenGL

example

format

• http://www.angelcode.com/products/bmfont/doc/file_format.html
• http://www.angelcode.com/products/bmfont/
• http://www.angelcode.com/products/bmfont/doc/render_text.html

usage

font, _ := bitmapfont.NewOpenGLFont("test_ubuntu.fnt", "test_ubuntu.png")
defer font.Delete()

multitext := `Bitmapfont
easy OpenGL font rendering
for Go`
txt := bitmapfont.NewText(multitext, 10, 10, 300, 100, font)

txt.Render()

TODO

• multi-byte chars
• optimize amount lookup

(c) 2016, http://ernestmicklei.com. MIT License

Documentation

Index

• type Char
• type Common
• type Font
  • func NewFont() *Font
  • func (f *Font) AmountBetween(left, right uint8) float32
  • func (f *Font) Base() float32
  • func (f *Font) CharAt(c uint8) Char
  • func (f *Font) LineHeight() float32
  • func (f *Font) Scales() (float32, float32)
  • func (f *Font) String() string
• type FontReader
  • func NewFontReader() *FontReader
  • func (r *FontReader) ReadFile(filename string) (*Font, error)
• type Info
• type Kerning
• type OpenGLFont
  • func NewOpenGLFont(fntFilename, imageFilename string) (*OpenGLFont, error)
  • func (f *OpenGLFont) Delete()
• type OpenGLTextureBuilder
  • func NewTextureBuilder() OpenGLTextureBuilder
  • func (r OpenGLTextureBuilder) BuildFromFile(filename string) (uint32, error)
• type Page
• type Text
  • func NewText(text string, leftTopX, leftTopY, width, height float32, font *OpenGLFont) Text
  • func (t Text) ActualWidth() float32
  • func (t Text) Centered() Text
  • func (t Text) Height() float32
  • func (t Text) Render()
  • func (t Text) Width() float32
• type TextureVertex

Types

type Char

type Char struct {
	Id       uint8   // The character id.
	X        float32 // The left position of the character image in the texture.
	Y        float32 // The top position of the character image in the texture.
	Width    float32 // The width of the character image in the texture.
	Height   float32 // The height of the character image in the texture.
	Xoffset  float32 // How much the current position should be offset when copying the image from the texture to the screen.
	Yoffset  float32 // How much the current position should be offset when copying the image from the texture to the screen.
	Xadvance float32 // How much the current position should be advanced after drawing the character.
	Page     int     //	The texture page where the character image is found.
	Channel  int     //	The texture channel where the character image is found (1 = blue, 2 = green, 4 = red, 8 = alpha, 15 = all channels).
	Letter   string  // The letter is represents
}

This tag describes on character in the font. There is one for each included character in the font.

type Common

type Common struct {
	LineHeight float32 // This is the distance in pixels between each line of text.
	Base       int     // The number of pixels from the absolute top of the line to the base of the characters.
	ScaleW     float32 // The width of the texture, normally used to scale the x pos of the character image.
	ScaleH     float32 // The height of the texture, normally used to scale the y pos of the character image.
	Pages      int     // The number of texture pages included in the font.
	Packed     int     // Set to 1 if the monochrome characters have been packed into each of the texture channels. In this case alphaChnl describes what is stored in each channel.
	AlphaChnl  int     // Set to 0 if the channel holds the glyph data, 1 if it holds the outline, 2 if it holds the glyph and the outline, 3 if its set to zero, and 4 if its set to one.
	RedChnl    int     // Set to 0 if the channel holds the glyph data, 1 if it holds the outline, 2 if it holds the glyph and the outline, 3 if its set to zero, and 4 if its set to one.
	GreenChnl  int     // Set to 0 if the channel holds the glyph data, 1 if it holds the outline, 2 if it holds the glyph and the outline, 3 if its set to zero, and 4 if its set to one.
	BlueChnl   int     // Set to 0 if the channel holds the glyph data, 1 if it holds the outline, 2 if it holds the glyph and the outline, 3 if its set to zero, and 4 if its set to one.
}

This tag holds information common to all characters.

type Font

type Font struct {
	Common Common
	// contains filtered or unexported fields
}

func NewFont

func NewFont() *Font

func (*Font) AmountBetween

func (f *Font) AmountBetween(left, right uint8) float32

func (*Font) Base

func (f *Font) Base() float32

func (*Font) CharAt

func (f *Font) CharAt(c uint8) Char

func (*Font) LineHeight

func (f *Font) LineHeight() float32

func (*Font) Scales

func (f *Font) Scales() (float32, float32)

func (*Font) String

func (f *Font) String() string

type FontReader

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

func NewFontReader

func NewFontReader() *FontReader

func (*FontReader) ReadFile

func (r *FontReader) ReadFile(filename string) (*Font, error)

type Info

type Info struct {
	Face     string // This is the name of the true type font.
	Size     int    // The size of the true type font.
	Bld      bool   // The font is bold.
	Italic   bool   // The font is italic.
	Charset  string // The name of the OEM charset used (when not unicode).
	Unicode  bool   // Set to 1 if it is the unicode charset.
	StretchH int    // The font height stretch in percentage. 100% means no stretch.
	Smooth   bool   // Set to 1 if smoothing was turned on.
	AA       int    // The supersampling level used. 1 means no supersampling was used.
	Padding  []int  // The padding for each character (up, right, down, left).
	Spacing  []int  // The spacing for each character (horizontal, vertical).
	Outline  int    // The outline thickness for the characters.
}

This tag holds information on how the font was generated.

type Kerning

type Kerning struct {
	First  uint8   // The first character id.
	Second uint8   // The second character id.
	Amount float32 // How much the x position should be adjusted when drawing the second character immediately following the first.
}

The kerning information is used to adjust the distance between certain characters, e.g. some characters should be placed closer to each other than others.

type OpenGLFont

type OpenGLFont struct {
	*Font
	// contains filtered or unexported fields
}

func NewOpenGLFont

func NewOpenGLFont(fntFilename, imageFilename string) (*OpenGLFont, error)

NewOpenGLFont createa a new font by reading the FNT and texture image file (PNG) This creates an OpenGL resource ; do not forget to call Delete() when no longer used.

func (*OpenGLFont) Delete

func (f *OpenGLFont) Delete()

type OpenGLTextureBuilder

type OpenGLTextureBuilder struct{}

func NewTextureBuilder

func NewTextureBuilder() OpenGLTextureBuilder

func (OpenGLTextureBuilder) BuildFromFile

func (r OpenGLTextureBuilder) BuildFromFile(filename string) (uint32, error)

type Page

type Page struct {
	Id   int    // The page id.
	File string // The texture file name.
}

This tag gives the name of a texture file. There is one for each page in the font.

type Text

type Text struct {
	X float32 // left-top x-coordinate
	Y float32 // left-top y-coordinate
	// contains filtered or unexported fields
}

func NewText

func NewText(text string, leftTopX, leftTopY, width, height float32, font *OpenGLFont) Text

NewText returns a new Text value for rendering a (multiline) string using a Font inside a 2D box. If the width is set to zero then the text will have a unscaled width computed from the text.

func (Text) ActualWidth

func (t Text) ActualWidth() float32

func (Text) Centered

func (t Text) Centered() Text

Centered returns a new text centered on its X and Y coordinate.

func (Text) Height

func (t Text) Height() float32

func (Text) Render

func (t Text) Render()

Render calls a function with 4 TextureVertex values per character. http://www.glprogramming.com/red/chapter09.html http://www.angelcode.com/products/bmfont/doc/render_text.html

func (Text) Width

func (t Text) Width() float32

type TextureVertex

type TextureVertex struct {
	S, T float32 // texture coordinates
	X, Y float32 // position coordinates
}

TextureVertex captures one corner of a character to render.