Change the aspect ratio of an image by repeating edge pixels

repeat_edge_pixels.py

pil_image = Image.open("test.png").convert('RGB')
result = Image.new(pil_image.mode, (w_target, h_target))
pad_x = (w_target-w_source)//2
result.paste(pil_image, (pad_x, 0))

sample = 8

left_side = pil_image.crop((0, 0, sample, h_source))
left_side = left_side.resize((1, h_source//2), Image.BILINEAR)
left_side = left_side.resize((pad_x, h_source), Image.BILINEAR)
result.paste(left_side, (0, 0))

right_side = pil_image.crop((w_source-sample, 0, w_source, h_source))
right_side = right_side.resize((1, h_source//2), Image.BILINEAR)
right_side = right_side.resize((w_source-pad_x, h_source), Image.BILINEAR)
result.paste(right_side, (w_target-pad_x, 0))

image_np = np.array(result, dtype=np.float32)
overlap = 32

alpha = np.arange(0, 1, 1.0/overlap, dtype=np.float32)
alpha = np.tile(alpha, [3, h_target, 1])
alpha = alpha.transpose(1, 2, 0)

left_np = np.array(left_side.resize((overlap, h_target)), dtype=np.float32)
right_np = np.array(right_side.resize((overlap, h_target)), dtype=np.float32)
image_np[:,pad_x:pad_x+overlap,:] = image_np[:,pad_x:pad_x+overlap,:] * alpha \
+ left_np * (1-alpha)
image_np[:,-pad_x-overlap:-pad_x,:] = image_np[:,-pad_x-overlap:-pad_x,:] * (1- alpha) \
+ right_np * alpha

pil_image_out = Image.fromarray(image_np.astype(np.uint8))