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with tf.variable_scope('_interpolate'):
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# constants
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num_batch = tf.shape(im)[0]
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height = tf.shape(im)[1]
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width = tf.shape(im)[2]
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channels = tf.shape(im)[3]
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x = tf.cast(x, 'float32')
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y = tf.cast(y, 'float32')
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height_f = tf.cast(height, 'float32')
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width_f = tf.cast(width, 'float32')
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out_height = out_size[0]
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out_width = out_size[1]
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zero = tf.zeros([], dtype='int32')
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max_y = tf.cast(tf.shape(im)[1] - 1, 'int32')
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max_x = tf.cast(tf.shape(im)[2] - 1, 'int32')
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x = tf.cast(_repeat2(tf.range(0, width), height * num_batch), 'float32') + x * WIDTH
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y = tf.cast(_repeat2(_repeat(tf.range(0, height), width), num_batch), 'float32') + y * HEIGHT
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# do sampling
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x0 = tf.cast(tf.floor(x), 'int32')
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x1 = x0 + 1
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y0 = tf.cast(tf.floor(y), 'int32')
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y1 = y0 + 1
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x0 = tf.clip_by_value(x0, zero, max_x)
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x1 = tf.clip_by_value(x1, zero, max_x)
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y0 = tf.clip_by_value(y0, zero, max_y)
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y1 = tf.clip_by_value(y1, zero, max_y)
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dim2 = width
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dim1 = width*height
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base = _repeat(tf.range(num_batch)*dim1, out_height*out_width)
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base_y0 = base + y0*dim2
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base_y1 = base + y1*dim2
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idx_a = base_y0 + x0
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idx_b = base_y1 + x0
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idx_c = base_y0 + x1
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idx_d = base_y1 + x1
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# use indices to lookup pixels in the flat image and restore
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# channels dim
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im_flat = tf.reshape(im, tf.stack([-1, channels]))
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im_flat = tf.cast(im_flat, 'float32')
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Ia = tf.gather(im_flat, idx_a)
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Ib = tf.gather(im_flat, idx_b)
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Ic = tf.gather(im_flat, idx_c)
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Id = tf.gather(im_flat, idx_d)
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# and finally calculate interpolated values
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x0_f = tf.cast(x0, 'float32')
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x1_f = tf.cast(x1, 'float32')
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y0_f = tf.cast(y0, 'float32')
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y1_f = tf.cast(y1, 'float32')
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wa = tf.expand_dims(((x1_f-x) * (y1_f-y)), 1)
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wb = tf.expand_dims(((x1_f-x) * (y-y0_f)), 1)
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wc = tf.expand_dims(((x-x0_f) * (y1_f-y)), 1)
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wd = tf.expand_dims(((x-x0_f) * (y-y0_f)), 1)
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output = tf.add_n([wa*Ia, wb*Ib, wc*Ic, wd*Id])
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return output
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def _meshgrid(height, width):
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with tf.variable_scope('_meshgrid'):
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# This should be equivalent to:
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# x_t, y_t = np.meshgrid(np.linspace(-1, 1, width),
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# np.linspace(-1, 1, height))
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# ones = np.ones(np.prod(x_t.shape))
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# grid = np.vstack([x_t.flatten(), y_t.flatten(), ones])
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x_t = tf.matmul(tf.ones(shape=tf.stack([height, 1])),
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tf.transpose(tf.expand_dims(tf.linspace(-1.0, 1.0, width), 1), [1, 0]))
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y_t = tf.matmul(tf.expand_dims(tf.linspace(-1.0, 1.0, height), 1),
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tf.ones(shape=tf.stack([1, width])))
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x_t_flat = tf.reshape(x_t, (1, -1))
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y_t_flat = tf.reshape(y_t, (1, -1))
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ones = tf.ones_like(x_t_flat)
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grid = tf.concat(axis=0, values=[x_t_flat, y_t_flat, ones])
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return grid
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def _transform(x_s, y_s, input_dim, out_size):
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with tf.variable_scope('_transform'):
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num_batch = tf.shape(input_dim)[0]
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height = tf.shape(input_dim)[1]
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width = tf.shape(input_dim)[2]
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num_channels = tf.shape(input_dim)[3]
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height_f = tf.cast(height, 'float32')
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width_f = tf.cast(width, 'float32')
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out_height = out_size[0]
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out_width = out_size[1]
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x_s_flat = tf.reshape(x_s, [-1])
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y_s_flat = tf.reshape(y_s, [-1])
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input_transformed = _interpolate(
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input_dim, x_s_flat, y_s_flat,
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out_size)
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