Fixes incoherence in affine transformation with center is defined as …

[vfdev-5]

Description:

• Fixes incoherence in the affine transformation when the center is defined as half image size + 0.5
• Incoherence is when affine transformation is 90 degrees rotation and output contains a zero line or row

For example:
Currently:

import torchvision
from torchvision.transforms.functional import affine
print(torchvision.__version__)

import numpy as np
from PIL import Image


img = np.arange(0, 3 * 12 * 12, dtype="uint8").reshape((3, 12, 12))
pil_img = Image.fromarray(img.transpose((1, 2, 0)))
out_pil_img = affine(pil_img, -90, (0, 0), scale=1.0, shear=(0, 0))
np.asarray(out_pil_img)[:, :, 0]

0.6.1+cu101
array([[  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0],
       [ 11,  23,  35,  47,  59,  71,  83,  95, 107, 119, 131, 143],
       [ 10,  22,  34,  46,  58,  70,  82,  94, 106, 118, 130, 142],
       [  9,  21,  33,  45,  57,  69,  81,  93, 105, 117, 129, 141],
       [  8,  20,  32,  44,  56,  68,  80,  92, 104, 116, 128, 140],
       [  7,  19,  31,  43,  55,  67,  79,  91, 103, 115, 127, 139],
       [  6,  18,  30,  42,  54,  66,  78,  90, 102, 114, 126, 138],
       [  5,  17,  29,  41,  53,  65,  77,  89, 101, 113, 125, 137],
       [  4,  16,  28,  40,  52,  64,  76,  88, 100, 112, 124, 136],
       [  3,  15,  27,  39,  51,  63,  75,  87,  99, 111, 123, 135],
       [  2,  14,  26,  38,  50,  62,  74,  86,  98, 110, 122, 134],
       [  1,  13,  25,  37,  49,  61,  73,  85,  97, 109, 121, 133]],
      dtype=uint8)

and with the fix it gives

0.8.0a0+9126078
array([[ 11,  23,  35,  47,  59,  71,  83,  95, 107, 119, 131, 143],
       [ 10,  22,  34,  46,  58,  70,  82,  94, 106, 118, 130, 142],
       [  9,  21,  33,  45,  57,  69,  81,  93, 105, 117, 129, 141],
       [  8,  20,  32,  44,  56,  68,  80,  92, 104, 116, 128, 140],
       [  7,  19,  31,  43,  55,  67,  79,  91, 103, 115, 127, 139],
       [  6,  18,  30,  42,  54,  66,  78,  90, 102, 114, 126, 138],
       [  5,  17,  29,  41,  53,  65,  77,  89, 101, 113, 125, 137],
       [  4,  16,  28,  40,  52,  64,  76,  88, 100, 112, 124, 136],
       [  3,  15,  27,  39,  51,  63,  75,  87,  99, 111, 123, 135],
       [  2,  14,  26,  38,  50,  62,  74,  86,  98, 110, 122, 134],
       [  1,  13,  25,  37,  49,  61,  73,  85,  97, 109, 121, 133],
       [  0,  12,  24,  36,  48,  60,  72,  84,  96, 108, 120, 132]],
      dtype=uint8)

[vfdev-5]

Just replaced corner case value scale=1.1 when a=90

[fmassa]

Thanks a lot!