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Python相机等效焦距转换

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摘要

用于转换 相机胶片 大小变化时的 等效焦距.

Python实现代码

CV大法好, 拷走就能用(

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# coding=utf-8
"""
Created by MineClever to convert camera film size
"""

from math import atan, sqrt

class MathCamFovConvert (object):
    AngleToRad = 0.017453292519943295
    RadToAngle = 57.29577951308232

    @classmethod
    def calcFovFormHeightWidth(cls, w, h, focusDist, bRadian=False):
        # type: (float, float, float, bool) -> tuple[float,float, float]
        """
        input :w = FilmWidth(mm), h = FilmHeight(mm), focusDist(mm) = Focus Distance, bRadian -> if return radian value.
        return : tuple(HFov, VFov, DFov)

        """
        dx = focusDist
        cx= w /2
        cy = h /2
        dy = sqrt(cx*cx + cy*cy)

        DFovHalf = atan(dy/dx)
        DFov = DFovHalf * 2
        HFov = atan(cx/dx) * 2
        VFov = atan(cy/dx) * 2

        if not bRadian:
            HFov *= cls.RadToAngle
            VFov *= cls.RadToAngle
            DFov *= cls.RadToAngle

        return (HFov, VFov, DFov)

    @classmethod
    def calcFocusDistSameLook (cls, oriW, oriH, tarW, tarH, oriFocusDist, bLockHFov=True, bRadian= False):
        # type:(float ,float, float, float, float, bool, bool)->tuple[float, float, float]
        """
        calcFocusDistSameLook calculate a new HFov, VFov, Focus Distance


        Arguments:
            oriW -- origin width of film back size ;
            oriH -- origin height of film back size ;
            tarW -- target new width of film back size ;
            tarH -- target new height of film back size;
            oriFocusDist -- origin focal distance to film back ;

        Keyword Arguments:
            bLockHFov -- use origin HFov as reference (default: {True})
            bRadian -- return value as radian one (default: {False})

        Returns:
            return new HFov, new VHFov , new focal distance to film back as a tuple
        """
        oriDx = oriFocusDist
        oriCx = oriW / 2
        oriCy = oriH / 2
        # oriDy = sqrt(oriCx * oriCx + oriCy * oriCy)

        oriHFovHalf = atan(oriCx / oriDx) # 1/2 HFov
        oriVFovHalf = atan(oriCy / oriDx) # 1/2 VFov

        newCx = tarW / 2
        newCy = tarH / 2


        # NOTE: We should keep one fov sticked at least
        if bLockHFov : # NOTE: change cy only
            # NOTE:  newCx / tan(HFov/2[angle]) -> new focus distance
            newDx = newCx / (oriCx / oriDx)

            # NOTE: Generate new VFov
            newVFovHalf = atan(newCy / newDx) # type: float
            newVFov = newVFovHalf * 2
            newHFov = oriHFovHalf * 2
        else: # NOTE: change cx only
            # NOTE:  newCy / tan(VFov/2[angle]) -> new focus distance
            newDx = newCy / (oriCy / oriDx)

            # NOTE: Generate new HFov
            newHFovHalf = atan(newCx / newDx)  # type: float
            newHFov = newHFovHalf * 2
            newVFov = oriVFovHalf * 2

        # NOTE : convert to angle
        if not bRadian:
            newHFov *= cls.RadToAngle
            newVFov *= cls.RadToAngle

        return (newHFov, newVFov, newDx)

实现原理

Img_01

IMG_02

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