diff options
Diffstat (limited to 'sixel.go')
| -rw-r--r-- | sixel.go | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/sixel.go b/sixel.go new file mode 100644 index 0000000..4e44c79 --- /dev/null +++ b/sixel.go @@ -0,0 +1,205 @@ +// Package sixel can be used to render image.Image to the terminal using +// various strategies (including sixel). +package sixel + +import ( + "bufio" + "fmt" + "image" + "image/color" + "image/color/palette" + "image/draw" + "io" +) + +func scale100(c uint32) int { + return int(c) * 100 / 0xffff +} + +var sixelPalette = append(color.Palette{color.Transparent}, palette.WebSafe...) + +// Print renders the given image as a sixel. +func Print(w io.Writer, img image.Image) error { + palettized := image.NewPaletted(img.Bounds(), sixelPalette) + draw.FloydSteinberg.Draw(palettized, palettized.Bounds(), img, image.Point{}) + bw := bufio.NewWriter(w) + if _, err := io.WriteString(bw, "\033P7;1q"); err != nil { + return err + } + for i, c := range sixelPalette[1:] { + r, g, b, _ := c.RGBA() + if _, err := fmt.Fprintf(bw, "#%d;2;%d;%d;%d", i, scale100(r), scale100(g), scale100(b)); err != nil { + return err + } + } + for row := 0; row < palettized.Bounds().Dy(); row++ { + y := palettized.Bounds().Min.Y + row + if row > 0 { + if row%6 == 0 { + if _, err := io.WriteString(bw, "-"); err != nil { + return err + } + } else { + if _, err := io.WriteString(bw, "$"); err != nil { + return err + } + } + } + for x := palettized.Bounds().Min.X; x < palettized.Bounds().Max.X; x++ { + c := palettized.ColorIndexAt(x, y) + if c == 0 { + if _, err := fmt.Fprint(bw, "?"); err != nil { + return err + } + } else { + char := '?' + 1<<(row%6) + if _, err := fmt.Fprintf(bw, "#%d%c", c-1, char); err != nil { + return err + } + } + } + } + if _, err := io.WriteString(bw, "\033\\"); err != nil { + return err + } + if err := bw.Flush(); err != nil { + return err + } + return nil +} + +func isFullyTransparent(c color.Color) bool { + _, _, _, a := c.RGBA() + return a == 0 +} + +// PrintBlock renders the given image using block characters. Yeah I know it's +// not a sixel but it could be used as a fallback if sixel isn't supported. +func PrintBlock(w io.Writer, img image.Image) error { + bw := bufio.NewWriter(w) + for row := 0; row < img.Bounds().Dy(); row += 2 { + y := img.Bounds().Min.Y + row + if row > 0 { + if _, err := io.WriteString(bw, "\n"); err != nil { + return err + } + } + for x := img.Bounds().Min.X; x < img.Bounds().Max.X; x++ { + hi := img.At(x, y) + if isFullyTransparent(hi) { + if y+1 >= img.Bounds().Max.Y || isFullyTransparent(img.At(x, y+1)) { + if _, err := io.WriteString(bw, "\033[49m "); err != nil { + return err + } + } else { + r, g, b, _ := img.At(x, y+1).RGBA() + if _, err := fmt.Fprintf(bw, "\033[38;2;%d;%d;%dm\033[49m▄", r>>8, g>>8, b>>8); err != nil { + return err + } + } + } else { + if y+1 < img.Bounds().Max.Y && !isFullyTransparent(img.At(x, y+1)) { + r, g, b, _ := img.At(x, y+1).RGBA() + if _, err := fmt.Fprintf(bw, "\033[48;2;%d;%d;%dm", r>>8, g>>8, b>>8); err != nil { + return err + } + } else { + if _, err := io.WriteString(bw, "\033[49m"); err != nil { + return err + } + } + r, g, b, _ := hi.RGBA() + if _, err := fmt.Fprintf(bw, "\033[38;2;%d;%d;%dm▀", r>>8, g>>8, b>>8); err != nil { + return err + } + } + } + if _, err := io.WriteString(bw, "\033[39m\033[49m"); err != nil { + return err + } + } + if err := bw.Flush(); err != nil { + return err + } + return nil +} + +type xtermColor int8 + +func (c xtermColor) RGBA() (r, g, b, a uint32) { + var col color.RGBA + switch c { + case 0: + col = color.RGBA{R: 0x00, G: 0x00, B: 0x00, A: 0xff} + case 1: + col = color.RGBA{R: 0xcd, G: 0x00, B: 0x00, A: 0xff} + case 2: + col = color.RGBA{R: 0x00, G: 0xcd, B: 0x00, A: 0xff} + case 3: + col = color.RGBA{R: 0xcd, G: 0xcd, B: 0x00, A: 0xff} + case 4: + col = color.RGBA{R: 0x00, G: 0x00, B: 0xee, A: 0xff} + case 5: + col = color.RGBA{R: 0xcd, G: 0x00, B: 0xcd, A: 0xff} + case 6: + col = color.RGBA{R: 0x00, G: 0xcd, B: 0xcd, A: 0xff} + case 7: + col = color.RGBA{R: 0xe5, G: 0xe5, B: 0xe5, A: 0xff} + case 60: + col = color.RGBA{R: 0x7f, G: 0x7f, B: 0x7f, A: 0xff} + case 61: + col = color.RGBA{R: 0xff, G: 0x00, B: 0x00, A: 0xff} + case 62: + col = color.RGBA{R: 0x00, G: 0xff, B: 0x00, A: 0xff} + case 63: + col = color.RGBA{R: 0xff, G: 0xff, B: 0x00, A: 0xff} + case 64: + col = color.RGBA{R: 0x5c, G: 0x5c, B: 0xff, A: 0xff} + case 65: + col = color.RGBA{R: 0xff, G: 0x00, B: 0xff, A: 0xff} + case 66: + col = color.RGBA{R: 0x00, G: 0xff, B: 0xff, A: 0xff} + case 67: + col = color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff} + default: + panic("not an xterm color") + } + return col.RGBA() +} + +var xtermPalette = color.Palette{color.Transparent, xtermColor(0), xtermColor(1), xtermColor(2), xtermColor(3), xtermColor(4), xtermColor(5), xtermColor(6), xtermColor(7), xtermColor(60), xtermColor(61), xtermColor(62), xtermColor(63), xtermColor(64), xtermColor(65), xtermColor(66), xtermColor(67)} + +// PrintXterm16 renders the given image using the basic XTerm 16 colors. This +// should have great compatibility and it looks pretty impressively bad. +func PrintXTerm16(w io.Writer, img image.Image) error { + palettized := image.NewPaletted(img.Bounds(), xtermPalette) + draw.FloydSteinberg.Draw(palettized, palettized.Bounds(), img, image.Point{}) + bw := bufio.NewWriter(w) + for row := 0; row < palettized.Bounds().Dy(); row++ { + y := palettized.Bounds().Min.Y + row + if row > 0 { + if _, err := io.WriteString(bw, "\n"); err != nil { + return err + } + } + for x := palettized.Bounds().Min.X; x < palettized.Bounds().Max.X; x++ { + c := palettized.At(x, y) + if c == color.Transparent { + if _, err := io.WriteString(bw, "\033[49m "); err != nil { + return err + } + } else { + if _, err := fmt.Fprintf(bw, "\033[%dm ", 40+c.(xtermColor)); err != nil { + return err + } + } + } + if _, err := io.WriteString(bw, "\033[49m"); err != nil { + return err + } + } + if err := bw.Flush(); err != nil { + return err + } + return nil +} |