80 lines
2.0 KiB
Go
80 lines
2.0 KiB
Go
package caption
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import (
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"image"
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"image/color"
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"github.com/golang/freetype/truetype"
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"golang.org/x/image/draw"
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"golang.org/x/image/font"
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"golang.org/x/image/math/fixed"
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)
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type Line struct {
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// collection of all text segments
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Data []Segment `json:"data"`
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// applies to all segments; avoid direct assignment and use SetFont instead
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Font []byte `json:"font"`
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// applies to all segments; avoid direct assignment and use SetFont instead
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Options *truetype.Options `json:"options"`
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// contains reference to parsed font, populated once per instance
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face font.Face
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}
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// SetFont clears line font cache and sets the new font.
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func (l *Line) SetFont(v []byte, opts *truetype.Options) { l.face = nil; l.Font = v; l.Options = opts }
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type Segment struct {
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Value string `json:"value"`
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Color color.Color `json:"color"`
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}
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// Render draws the current contents of Line on [draw.Image].
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func (l *Line) Render(ctx *Context, frame draw.Image, x, y int) error {
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face := l.face
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if face == nil {
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if len(l.Font) != 0 {
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// parse & cache Line font
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if err := l.cacheFont(l.Font); err != nil {
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return err
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}
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return l.Render(ctx, frame, x, y)
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}
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// fall back to default font
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if l.Options != nil { // global default: Options is not zero
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// cache global default without clobbering Line font
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if err := l.cacheFont(defaultFont); err != nil {
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return err // unreachable
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}
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return l.Render(ctx, frame, x, y)
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}
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// fast path: Font and Options are zero
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if err := ctx.parseFont(); err != nil {
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return err
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}
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face = ctx.defaultFont
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}
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drawer := &font.Drawer{Dst: frame, Face: face, Dot: fixed.Point26_6{X: fixed.I(x), Y: fixed.I(y)}}
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for _, seg := range l.Data {
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drawer.Src = image.NewUniform(seg.Color)
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drawer.DrawString(seg.Value)
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}
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return nil
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}
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// cacheFont parses truetype font data v and stores the result in Line.
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// The cache is invalidated by SetFont.
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func (l *Line) cacheFont(v []byte) error {
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f, err := truetype.Parse(v)
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if err == nil {
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l.face = truetype.NewFace(f, l.Options)
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}
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return err
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}
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