Documentation
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Overview ¶
Package mct implements the Multi-Component Transform (MCT) defined by ISO/IEC 15444-1 §F.4.9 for JPEG 2000.
Two transforms are specified:
- RCT (Reversible Component Transform): integer-to-integer, used in conjunction with the 5/3 reversible wavelet. It is exactly reversible on integer inputs of arbitrary precision.
- ICT (Irreversible Component Transform): floating-point, used with the 9/7 irreversible wavelet. It is the standard BT.601 / JFIF Y'CbCr matrix and is round-trip accurate to within float64 rounding.
Both transforms operate on three components (R, G, B). The JPEG 2000 codestream COD marker's MCT flag indicates whether to apply them; the choice of transform is derived from the wavelet kernel: 5/3 → RCT, 9/7 → ICT.
Reference: ISO/IEC 15444-1:2019 §F.4.9 (Equations F.25 through F.32).
Index ¶
- func ForwardICT(r, g, b, y, cb, cr []float64)
- func ForwardICTInPlace(r, g, b []float64)
- func ForwardRCT(r, g, b, y, u, v []int32)
- func ForwardRCTInPlace(r, g, b []int32)
- func InverseICT(y, cb, cr, r, g, b []float64)
- func InverseICTInPlace(r, g, b []float64)
- func InverseRCT(y, u, v, r, g, b []int32)
- func InverseRCTInPlace(r, g, b []int32)
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func ForwardICT ¶
func ForwardICT(r, g, b, y, cb, cr []float64)
ForwardICT applies the irreversible component transform (BT.601 / JFIF matrix) to R, G, B producing Y, Cb, Cr floating-point components. All slice arguments must have the same length.
Y = 0.299*R + 0.587*G + 0.114*B Cb = -0.16875*R - 0.33126*G + 0.5*B Cr = 0.5*R - 0.41869*G - 0.08131*B
func ForwardICTInPlace ¶
func ForwardICTInPlace(r, g, b []float64)
ForwardICTInPlace is the float64 analogue of ForwardRCTInPlace.
func ForwardRCT ¶
func ForwardRCT(r, g, b, y, u, v []int32)
ForwardRCT applies the reversible component transform to interleaved or planar R, G, B components and writes the results into y, u, v. All four slice arguments must have the same length (the number of samples per component).
Y = ⌊(R + 2G + B) / 4⌋ U = B − G V = R − G
The transform is exactly invertible by InverseRCT.
func ForwardRCTInPlace ¶
func ForwardRCTInPlace(r, g, b []int32)
ForwardRCTInPlace is a convenience wrapper that rewrites the R, G, B component slices with the Y, U, V output. The caller passes the same three slices; on return r holds Y, g holds U, b holds V.
func InverseICT ¶
func InverseICT(y, cb, cr, r, g, b []float64)
InverseICT applies the inverse irreversible component transform, recovering R, G, B from Y, Cb, Cr. All slice arguments must have the same length.
R = Y + 1.402*Cr G = Y - 0.34413*Cb - 0.71414*Cr B = Y + 1.772*Cb
func InverseICTInPlace ¶
func InverseICTInPlace(r, g, b []float64)
InverseICTInPlace is the in-place inverse of ForwardICTInPlace.
func InverseRCT ¶
func InverseRCT(y, u, v, r, g, b []int32)
InverseRCT applies the inverse reversible component transform, recovering R, G, B from Y, U, V components. All six slice arguments must have the same length.
G = Y − ⌊(U + V) / 4⌋ R = V + G B = U + G
InverseRCT(ForwardRCT(R,G,B)) is the identity for every int32 input.
func InverseRCTInPlace ¶
func InverseRCTInPlace(r, g, b []int32)
InverseRCTInPlace is the in-place inverse of ForwardRCTInPlace. On entry r holds Y, g holds U, b holds V; on return r/g/b hold the recovered R/G/B.
Types ¶
This section is empty.
Source Files