Skip to content

ChromProcessor

Chrominance-based rPPG method introduced by de Haan & Jeanne (2013).

de Haan, G., & Jeanne, V. (2013). Robust Pulse Rate From Chrominance-Based rPPG. IEEE Transactions on Biomedical Engineering, 60(10), 2878-2886. https://doi.org/10.1109/TBME.2013.2266196

ChromProcessor

Bases: Processor

Chrominance-based rPPG algorithm by de Haan & Jeanne (2013).

Parameters:

Name Type Description Default
winsize int

window size for moving average calculations. Defaults to 45.

 45
method Literal['fixed', 'xovery']

method to use. Can be 'xovery' or 'fixed'. Defaults to "xovery".

 'xovery'
Source code in src\yarppg\processors\chrom.py 
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
class ChromProcessor(Processor):
    """Chrominance-based rPPG algorithm by de Haan & Jeanne (2013).

    Args:
        winsize: window size for moving average calculations. Defaults to 45.
        method: method to use. Can be 'xovery' or 'fixed'. Defaults to "xovery".
    """

    def __init__(
        self, winsize: int = 45, method: Literal["fixed", "xovery"] = "xovery"
    ):
        Processor.__init__(self)

        self.winsize = winsize
        self.method = method

        self._rgbs: list[Color] = []
        self._xs: list[float] = []
        self._ys: list[float] = []

    def process(self, roi: RegionOfInterest) -> RppgResult:
        """Calculate pulse signal update according to Chrom algorithm."""
        result = super().process(roi)
        self._rgbs.append(result.roi_mean)

        if self.method == "fixed":
            result.value = self._calculate_fixed_update()

        elif self.method == "xovery":
            result.value = self._calculate_xovery_update()

        return result

    def _calculate_fixed_update(self) -> float:
        rgbmean = Color.from_array(np.mean(self._rgbs[-self.winsize :], axis=0))

        rn = self._rgbs[-1].r / (rgbmean.r or 1.0)
        gn = self._rgbs[-1].g / (rgbmean.g or 1.0)
        bn = self._rgbs[-1].b / (rgbmean.b or 1.0)

        self._xs.append(3 * rn - 2 * gn)
        self._ys.append(1.5 * rn + gn - 1.5 * bn)

        return self._xs[-1] / (self._ys[-1] or 1.0) - 1

    def _calculate_xovery_update(self) -> float:
        rgb = self._rgbs[-1]

        self._xs.append(rgb.r - rgb.g)
        self._ys.append(0.5 * rgb.r + 0.5 * rgb.g - rgb.b)

        xmean = np.mean(self._xs[-self.winsize :])
        ymean = np.mean(self._ys[-self.winsize :])

        return float(xmean / (ymean or 1) - 1)

    def reset(self):
        """Reset internal state and intermediate values."""
        self._rgbs.clear()
        self._xs.clear()
        self._ys.clear()

process(roi)

Calculate pulse signal update according to Chrom algorithm.

Source code in src\yarppg\processors\chrom.py 
36
37
38
39
40
41
42
43
44
45
46
47
def process(self, roi: RegionOfInterest) -> RppgResult:
    """Calculate pulse signal update according to Chrom algorithm."""
    result = super().process(roi)
    self._rgbs.append(result.roi_mean)

    if self.method == "fixed":
        result.value = self._calculate_fixed_update()

    elif self.method == "xovery":
        result.value = self._calculate_xovery_update()

    return result

reset()

Reset internal state and intermediate values.

Source code in src\yarppg\processors\chrom.py 
72
73
74
75
76
def reset(self):
    """Reset internal state and intermediate values."""
    self._rgbs.clear()
    self._xs.clear()
    self._ys.clear()