feat: change offset in naive DCT

antecedent/jpeg_toolbox.py

@@ -206,7 +206,7 @@ def jpeg_fdct_naive(blocks: np.ndarray) -> np.ndarray:
     Returns: an array with the same shape as blocks with DCT values.
     """
     blocks = blocks.astype(float)
-    return dctn(blocks, axes=(-2, -1), norm='ortho')
+    return dctn(blocks - 128, axes=(-2, -1), norm='ortho')
 
 
 def jpeg_idct_naive(blocks: np.ndarray, quant_tbl: np.ndarray) -> np.ndarray:
@@ -218,7 +218,7 @@ def jpeg_idct_naive(blocks: np.ndarray, quant_tbl: np.ndarray) -> np.ndarray:
 
     Returns: an array with the same shape as blocks with DCT values.
     """
-    blocks = blocks.astype(float)
+    blocks = blocks.astype(float) + 128
     return idctn(blocks * quant_tbl.astype(np.uint16), axes=(-2, -1), norm='ortho')
 
 

antecedent/pipeline.py

@@ -131,11 +131,11 @@ class NaivePipeline(JPEGPipeline):
         return name == 'naive'
 
     def dct(self, blocks):
-        return quantize_naive_fdct(jpeg_fdct_naive(blocks - 128), quant_tbl=self.quant_tbl[:blocks.shape[1]],
+        return quantize_naive_fdct(jpeg_fdct_naive(blocks), quant_tbl=self.quant_tbl[:blocks.shape[1]],
                                    return_int=self.return_rounded)
 
     def idct(self, blocks):
-        return jpeg_idct_naive(blocks, self.quant_tbl[:blocks.shape[1]]) + 128
+        return jpeg_idct_naive(blocks, self.quant_tbl[:blocks.shape[1]])
 
 
 class IslowPipeline(JPEGPipeline):