178 lines
5.2 KiB
Go
178 lines
5.2 KiB
Go
package colorspace
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"strconv"
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"strings"
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)
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// SubsamplingScheme The subsampling scheme is commonly expressed as a three-part ratio J : A : B (e.g. 4:2:2), that describe the number of luminance and chrominance samples in a conceptual region that is J pixels wide and 2 pixels high.
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type SubsamplingScheme struct {
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// J horizontal sampling reference (width of the conceptual region). Usually, 4.
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J byte
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// A number of chrominance samples (Cb, Cr) in the first row of J pixels.
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A byte
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// B number of changes of chrominance samples (Cb, Cr) between first and second row of J pixels. Note that B has to be either zero or equal to A
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B byte
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}
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type ColorSpace struct {
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Subsampling SubsamplingScheme
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BitDepth byte
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}
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func (c ColorSpace) ToInteger() uint32 {
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return binary.BigEndian.Uint32([]byte{c.Subsampling.J, c.Subsampling.A, c.Subsampling.B, c.BitDepth})
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}
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// ElementPixels returns the number of pixels for a full element
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func (c ColorSpace) ElementPixels() int {
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return int(c.Subsampling.J) * 2
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}
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// ElementSamples returns the number of actual samples (total Y, Cb, Cr) for an encoded element
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func (c ColorSpace) ElementSamples() int {
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return int(c.Subsampling.J)*2 + c.ElementChromaSamples()
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}
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func (c ColorSpace) ElementChromaSamples() int {
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return int(c.Subsampling.A)*2 + int(c.Subsampling.B)*2
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}
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func (c ColorSpace) PlaneLumaSamples(width, height int) int {
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return width * height
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}
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func (c ColorSpace) PlaneCrSamples(width, height int) int {
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return int((int64(width) * int64(height) * (int64(c.Subsampling.A) + int64(c.Subsampling.B))) / int64(c.ElementPixels()))
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}
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func (c ColorSpace) PlaneCbSamples(width, height int) int {
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return int((int64(width) * int64(height) * (int64(c.Subsampling.A) + int64(c.Subsampling.B))) / int64(c.ElementPixels()))
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}
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func (c ColorSpace) FrameSizePacked(width, height int) (int, error) {
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a1 := int64(width) * int64(height)
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a2 := int64(c.ElementPixels())
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if a1%a2 != 0 {
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return 0, errors.New("not divisible pixels")
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}
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a3 := (a1 / a2) * int64(c.ElementSamples()) * int64(c.BitDepth)
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if a3%8 != 0 {
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return 0, errors.New("not divisible size")
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}
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return int(a3 / 8), nil
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}
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func (c ColorSpace) FrameSize(width, height int) (int, error) {
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actualBitDepth := int64(c.BitDepth)
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if actualBitDepth&0b111 != 0 {
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actualBitDepth = ((actualBitDepth + 8) >> 3) << 3
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}
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a1 := int64(width) * int64(height)
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a2 := int64(c.ElementPixels())
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if a1%a2 != 0 {
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return 0, errors.New("not divisible pixels")
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}
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a3 := (a1 / a2) * int64(c.ElementSamples()) * actualBitDepth
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if a3%8 != 0 {
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return 0, errors.New("not divisible size")
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}
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return int(a3 / 8), nil
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}
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func (c ColorSpace) check() error {
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if c.Subsampling.J <= 0 {
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return fmt.Errorf("unsupported J %d", c.Subsampling.J)
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}
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if c.Subsampling.A < 0 && c.Subsampling.A > c.Subsampling.J {
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return fmt.Errorf("unsupported A %d", c.Subsampling.A)
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}
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if c.Subsampling.B != 0 && c.Subsampling.B != c.Subsampling.A {
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return fmt.Errorf("unsupported B %d", c.Subsampling.B)
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}
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if c.BitDepth != 8 && c.BitDepth != 10 && c.BitDepth != 12 && c.BitDepth != 14 && c.BitDepth != 16 {
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return fmt.Errorf("unsupported BitDepth %d", c.BitDepth)
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}
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return nil
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}
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func NewColorSpaceFromInteger(colorSpace uint32) (ColorSpace, error) {
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buf := make([]byte, 4)
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binary.BigEndian.PutUint32(buf, colorSpace)
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space := ColorSpace{
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Subsampling: SubsamplingScheme{
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J: buf[0],
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A: buf[1],
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B: buf[2],
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},
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BitDepth: buf[3],
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}
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return space, space.check()
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}
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func NewColorSpaceFromString(colorSpace string) (ColorSpace, error) {
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colorSpace = strings.ToLower(colorSpace)
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if colorSpace == "420mpeg2" {
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return NewColorSpaceFromString("420p8")
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}
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splits := strings.Split(colorSpace, "p")
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if len(splits) == 1 { //default 8 bit
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splits = append(splits, "8")
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}
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space := ColorSpace{}
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switch strings.ReplaceAll(splits[0], ":", "") {
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case "420":
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space.Subsampling.J = 4
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space.Subsampling.A = 2
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space.Subsampling.B = 0
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case "422":
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space.Subsampling.J = 4
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space.Subsampling.A = 2
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space.Subsampling.B = 2
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case "444":
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space.Subsampling.J = 4
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space.Subsampling.A = 4
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space.Subsampling.B = 4
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default:
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return space, fmt.Errorf("unsupported Chroma Subsampling %s", splits[0])
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}
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n, err := strconv.Atoi(splits[1])
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if err != nil {
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return space, err
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}
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space.BitDepth = byte(n)
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return space, space.check()
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}
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func newColorSpaceFromStringInternal(colorSpace string) ColorSpace {
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space, _ := NewColorSpaceFromString(colorSpace)
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return space
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}
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var (
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Space420 ColorSpace = newColorSpaceFromStringInternal("420")
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Space422 ColorSpace = newColorSpaceFromStringInternal("422")
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Space444 ColorSpace = newColorSpaceFromStringInternal("444")
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Space420P10 ColorSpace = newColorSpaceFromStringInternal("420p10")
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Space422P10 ColorSpace = newColorSpaceFromStringInternal("422p10")
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Space444P10 ColorSpace = newColorSpaceFromStringInternal("444p10")
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Space420P12 ColorSpace = newColorSpaceFromStringInternal("420p12")
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Space422P12 ColorSpace = newColorSpaceFromStringInternal("422p12")
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Space444P12 ColorSpace = newColorSpaceFromStringInternal("444p12")
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Space420P16 ColorSpace = newColorSpaceFromStringInternal("420p16")
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Space422P16 ColorSpace = newColorSpaceFromStringInternal("422p16")
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Space444P16 ColorSpace = newColorSpaceFromStringInternal("444p16")
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)
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