limage - misc.go

     1  // Package limage introduces structures to read and build layered images.
     2  package limage
     3  
     4  import (
     5  	"image"
     6  	"image/color"
     7  	"strings"
     8  
     9  	"vimagination.zapto.org/limage/internal"
    10  )
    11  
    12  // MaskedImage represents an image that has a to-be-applied mask.
    13  type MaskedImage struct {
    14  	image.Image
    15  	Mask *image.Gray
    16  }
    17  
    18  // At returns the colour at the specified coords after masking.
    19  func (m MaskedImage) At(x, y int) color.Color {
    20  	return transparency(m.Image.At(x, y), m.Mask.GrayAt(x, y).Y)
    21  }
    22  
    23  // Text represents a text layer.
    24  type Text struct {
    25  	image.Image
    26  	TextData
    27  }
    28  
    29  // TextData represents the stylised text.
    30  type TextData []TextDatum
    31  
    32  // String returns a flattened string.
    33  func (t TextData) String() string {
    34  	var sb strings.Builder
    35  
    36  	for _, d := range t {
    37  		sb.WriteString(d.Data)
    38  	}
    39  
    40  	return sb.String()
    41  }
    42  
    43  // TextDatum is a collection of styling for a single piece of text.
    44  type TextDatum struct {
    45  	ForeColor, BackColor                   color.Color
    46  	Size, LetterSpacing, Rise              uint32
    47  	Bold, Italic, Underline, Strikethrough bool
    48  	Font, Data                             string
    49  }
    50  
    51  func transparency(ac color.Color, ao uint8) color.Color {
    52  	if ao == 0xff {
    53  		return ac
    54  	} else if ao == 0 {
    55  		return color.NRGBA64{}
    56  	}
    57  
    58  	c := internal.ColourToNRGBA(ac)
    59  	o := uint32(ao)
    60  	o |= o << 8
    61  	c.A = uint16(o * uint32(c.A) / 0xffff)
    62  
    63  	return c
    64  }
    65