[Image-SIG] About PIL.Image.Image.rotate method refinement

[Jhonlier Suarez Molina]

When I was using PIL.Image.Image.rotate (expand=True) to make a sequence 
of rotations to be joined later in a clip; but I found a trouble: my 
object vibrates because the resulting vertex move around the expected 
vertex. This is harmful for animations because you get undesirable 
tremble. So I try the problem forcing the resulting surface size to be 
odd in both dimentions, because the middle of these "odd" surfaces is 
exactly a pixel, not a pixel given for rounding. Remember that the 
middle of  1 2 3 4 5 6 7 8 9 clearly is  5, but the center of 1 2 3 4 is 
"somewhere" beetwen 2 and 3.

I rewrite the "rotate" method:

    def rotate(self, angle, resample=NEAREST, expand=0):
        "Rotate image.  Angle given as degrees counter-clockwise."

        if expand:
            import math
            angle = -angle * math.pi / 180
            matrix = [
                 math.cos(angle), math.sin(angle), 0.0,
                -math.sin(angle), math.cos(angle), 0.0
                 ]
            def transform(x, y, (a, b, c, d, e, f)=matrix):
                return a*x + b*y + c, d*x + e*y + f

            # calculate output size
            w, h = self.size
            xx = []
            yy = []
            for x, y in ((0, 0), (w, 0), (w, h), (0, h)):
                x, y = transform(x, y)
                xx.append(x)
                yy.append(y)
            w = int(math.ceil(max(xx)) - math.floor(min(xx)))
            h = int(math.ceil(max(yy)) - math.floor(min(yy)))

            # adjust center
            x, y = transform(w / 2.0, h / 2.0)
            matrix[2] = self.size[0] / 2.0 - x
            matrix[5] = self.size[1] / 2.0 - y

            return self.transform((w, h), AFFINE, matrix)

        if resample not in (NEAREST, BILINEAR, BICUBIC):
            raise ValueError("unknown resampling filter")

        self.load()

        if self.mode in ("1", "P"):
            resample = NEAREST

        return self._new(self.im.rotate(angle, resample))

for this:

    def rotate(self, angle, resample=NEAREST, expand=0):
        "Rotate image.  Angle given as degrees counter-clockwise."

        if expand:
            import math
            angle = -angle * math.pi / 180
            matrix = [
                 math.cos(angle), math.sin(angle), 0.0,
                -math.sin(angle), math.cos(angle), 0.0
                 ]
            def transform(x, y, (a, b, c, d, e, f)=matrix):
                return a*x + b*y + c, d*x + e*y + f

            # calculate output size
            w0, h0 = w, h = self.size
            xx = []
            yy = []
            for x, y in ((0, 0), (w, 0), (w, h), (0, h)):
                x, y = transform(x, y)
                xx.append(x)
                yy.append(y)
            w = int(math.ceil(max(xx)) - math.floor(min(xx)))
            if w & 1== 0:
                w += 1
            h = int(math.ceil(max(yy)) - math.floor(min(yy)))
            if h & 1== 0:
                h += 1

            # adjust center
            x, y = transform(w / 2.0, h / 2.0)
            matrix[2] = w0 / 2.0 - x
            matrix[5] = h0 / 2.0 - y

            return self.transform((w, h), AFFINE, matrix)

        if resample not in (NEAREST, BILINEAR, BICUBIC):
            raise ValueError("unknown resampling filter")

        self.load()

        if self.mode in ("1", "P"):
            resample = NEAREST

        return self._new(self.im.rotate(angle, resample))

This really works I am using it now and no more Parkinson in my animations.

Saludos,
Jhonlier

-- 



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