Add option to quantize per-tensor (ultralytics#12516)

* Add option to quantize per-tensor

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Glenn Jocher <[email protected]>

Author: 3 people

export.py

@@ -448,7 +448,8 @@ def export_pb(keras_model, file, prefix=colorstr('TensorFlow GraphDef:')):
 
 
 @try_export
-def export_tflite(keras_model, im, file, int8, data, nms, agnostic_nms, prefix=colorstr('TensorFlow Lite:')):
+def export_tflite(keras_model, im, file, int8, per_tensor, data, nms, agnostic_nms,
+                  prefix=colorstr('TensorFlow Lite:')):
     # YOLOv5 TensorFlow Lite export
     import tensorflow as tf
 
@@ -469,6 +470,8 @@ def export_tflite(keras_model, im, file, int8, data, nms, agnostic_nms, prefix=c
         converter.inference_input_type = tf.uint8  # or tf.int8
         converter.inference_output_type = tf.uint8  # or tf.int8
         converter.experimental_new_quantizer = True
+        if per_tensor:
+            converter._experimental_disable_per_channel = True
         f = str(file).replace('.pt', '-int8.tflite')
     if nms or agnostic_nms:
         converter.target_spec.supported_ops.append(tf.lite.OpsSet.SELECT_TF_OPS)
@@ -713,6 +716,7 @@ def run(
         keras=False,  # use Keras
         optimize=False,  # TorchScript: optimize for mobile
         int8=False,  # CoreML/TF INT8 quantization
+        per_tensor=False,  # TF per tensor quantization
         dynamic=False,  # ONNX/TF/TensorRT: dynamic axes
         simplify=False,  # ONNX: simplify model
         opset=12,  # ONNX: opset version
@@ -798,7 +802,14 @@ def run(
         if pb or tfjs:  # pb prerequisite to tfjs
             f[6], _ = export_pb(s_model, file)
         if tflite or edgetpu:
-            f[7], _ = export_tflite(s_model, im, file, int8 or edgetpu, data=data, nms=nms, agnostic_nms=agnostic_nms)
+            f[7], _ = export_tflite(s_model,
+                                    im,
+                                    file,
+                                    int8 or edgetpu,
+                                    per_tensor,
+                                    data=data,
+                                    nms=nms,
+                                    agnostic_nms=agnostic_nms)
             if edgetpu:
                 f[8], _ = export_edgetpu(file)
             add_tflite_metadata(f[8] or f[7], metadata, num_outputs=len(s_model.outputs))
@@ -837,6 +848,7 @@ def parse_opt(known=False):
     parser.add_argument('--keras', action='store_true', help='TF: use Keras')
     parser.add_argument('--optimize', action='store_true', help='TorchScript: optimize for mobile')
     parser.add_argument('--int8', action='store_true', help='CoreML/TF/OpenVINO INT8 quantization')
+    parser.add_argument('--per-tensor', action='store_true', help='TF per-tensor quantization')
     parser.add_argument('--dynamic', action='store_true', help='ONNX/TF/TensorRT: dynamic axes')
     parser.add_argument('--simplify', action='store_true', help='ONNX: simplify model')
     parser.add_argument('--opset', type=int, default=17, help='ONNX: opset version')