Fix the issue ivy-llc#15056

ivy/functional/frontends/paddle/nn/functional/vision.py

@@ -170,3 +170,83 @@ def pixel_shuffle(x, upscale_factor, data_format="NCHW"):
     return ivy.reshape(
         ivy.permute_dims(input_reshaped, (0, 1, 4, 2, 5, 3)), (b, oh, ow, oc)
     )
+
+
+"Add NN Vision Functions to Paddle Frontend "
+
+def grid_sample(input, grid, mode='bilinear', padding_mode='zeros'):
+    """
+    Samples elements from the input tensor using bilinear or nearest-neighbor sampling.
+    :param input: The input tensor of shape (batch_size, channels, height, width).
+    :param grid: The sampling grid of shape (batch_size, height, width, 2).
+    :param mode: The sampling mode - 'bilinear' or 'nearest'. Default is 'bilinear'.
+    :param padding_mode: The padding mode when grid values are out-of-bounds. Supports 'zeros' and 'border'.
+    :return: The sampled output tensor.
+    """
+
+    # Bilinear sampling
+    if mode == 'bilinear':
+        # Extract dimensions
+        B, C, H, W = input.shape
+        _, H_prime, W_prime, _ = grid.shape
+
+        # Normalize the grid values to be in the range [-1, 1]
+        grid = 2.0 * grid / torch.tensor([W - 1, H - 1], dtype=torch.float32) - 1.0
+
+        # Map grid points to pixel indices
+        grid = (grid + 1) * torch.tensor([W - 1, H - 1], dtype=torch.float32) / 2
+        grid_floor = torch.floor(grid).long()
+        grid_ceil = grid_floor + 1
+
+        # Get pixel values at grid points
+        indices_tl = grid_floor[..., 1, :, :].clamp(0, H - 1), grid_floor[..., 0, :, :].clamp(0, W - 1)
+        indices_tr = grid_floor[..., 1, :, :].clamp(0, H - 1), grid_ceil[..., 0, :, :].clamp(0, W - 1)
+        indices_bl = grid_ceil[..., 1, :, :].clamp(0, H - 1), grid_floor[..., 0, :, :].clamp(0, W - 1)
+        indices_br = grid_ceil[..., 1, :, :].clamp(0, H - 1), grid_ceil[..., 0, :, :].clamp(0, W - 1)
+
+        values_tl = input[..., indices_tl[0], indices_tl[1]]
+        values_tr = input[..., indices_tr[0], indices_tr[1]]
+        values_bl = input[..., indices_bl[0], indices_bl[1]]
+        values_br = input[..., indices_br[0], indices_br[1]]
+
+        # Calculate bilinear interpolation weights
+        wa = ((grid[..., 0, :, :] - indices_tl[1].float()) * (grid[..., 1, :, :] - indices_tl[0].float())).unsqueeze(1)
+        wb = ((indices_tr[1].float() - grid[..., 0, :, :]) * (grid[..., 1, :, :] - indices_tr[0].float())).unsqueeze(1)
+        wc = ((grid[..., 0, :, :] - indices_bl[1].float()) * (indices_bl[0].float() - grid[..., 1, :, :])).unsqueeze(1)
+        wd = ((indices_br[1].float() - grid[..., 0, :, :]) * (indices_br[0].float() - grid[..., 1, :, :])).unsqueeze(1)
+
+        output = wa * values_tl + wb * values_tr + wc * values_bl + wd * values_br
+
+    # Nearest-neighbor sampling
+    elif mode == 'nearest':
+        # Round the grid values to get the closest integer indices
+        x_rounded = torch.round(grid[..., 0]).long()
+        y_rounded = torch.round(grid[..., 1]).long()
+
+        if padding_mode == 'zeros':
+            # Create masks for out-of-bound x and y positions
+            mask_x = torch.logical_or(x_rounded < 0, x_rounded >= W)
+            mask_y = torch.logical_or(y_rounded < 0, y_rounded >= H)
+
+            # Using the indices, gather the values from the input tensor
+            sampled_output = input[..., y_rounded, x_rounded]
+
+            # Use the mask to set out-of-bound positions in the output to zero
+            sampled_output = torch.where(mask_x | mask_y, torch.zeros_like(sampled_output), sampled_output)
+
+        elif padding_mode == 'border':
+            # Clamp the indices to lie within the borders
+            x_clamped = torch.clamp(x_rounded, 0, W - 1)
+            y_clamped = torch.clamp(y_rounded, 0, H - 1)
+
+            # Using the clamped indices, gather the values from the input tensor
+            sampled_output = input[..., y_clamped, x_clamped]
+
+        else:
+            raise ValueError("Unsupported padding_mode. Expected 'zeros' or 'border'.")
+
+    else:
+        raise ValueError("Unsupported mode. Expected 'bilinear' or 'nearest'.")
+
+    return sampled_output
+