Opt: use ONNX model converted from MXNet for faster OCR

config/deploy.template.yaml

@@ -79,6 +79,10 @@ Deploy:
     # Address of ocr server for alas instance to connect
     # [Default] 127.0.0.1:22268
     OcrClientAddress: 127.0.0.1:22268
+    # Use ONNX Runtime for OCR inference instead of MXNet
+    # Requires onnxruntime package and model.onnx in each model directory
+    # [Default] false
+    UseOcrOnnx: false
 
   Update:
     # Use auto update and builtin updater feature

deploy/config.py

@@ -35,6 +35,7 @@ class ConfigModel:
     StartOcrServer: bool = False
     OcrServerPort: int = 22268
     OcrClientAddress: str = "127.0.0.1:22268"
+    UseOcrOnnx: bool = False
 
     # Update
     EnableReload: bool = True

dev_tools/convert_mxnet_to_onnx.py

@@ -0,0 +1,607 @@
+"""
+Convert MXNet cnocr checkpoints to ONNX format.
+
+Builds equivalent ONNX graphs directly from the MXNet symbol JSON and
+parameter files.  MXNet's built-in ONNX exporter cannot handle the
+hybridized bidirectional GRU (internal ops _rnn_param_concat + RNN),
+so the graph is reconstructed node-by-node.
+
+Output is written alongside the source checkpoint as model.onnx.
+
+The MODELS list at the bottom of this file defines which models to
+convert.  Each entry specifies the model name, directory, checkpoint
+prefix, and epoch.  Edit this list to add or remove models.
+
+Notes:
+- MXNet GRU gate order is [r, z, h]; ONNX expects [z, r, h].
+- MXNet Reshape shape values -2, -3 (relative dimensions) are rewritten 
+  because ONNX only supports -1.
+"""
+import os, sys, json
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+import numpy as np
+import onnx
+from onnx import helper, TensorProto, numpy_helper
+
+import mxnet as mx
+
+OPSET = 13
+FLOAT = TensorProto.FLOAT
+INT64 = TensorProto.INT64
+
+
+def parse_tuple(s):
+    """Parse '(1, 2)' or '()' string into tuple of ints."""
+    s = s.strip().strip('()')
+    if not s:
+        return ()
+    return tuple(int(x.strip()) for x in s.split(','))
+
+
+def ndarr(arr):
+    """numpy array -> ONNX initializer."""
+    return numpy_helper.from_array(arr.astype(np.float32))
+
+
+def shape_init(name, vals):
+    """Create an INT64 initializer for shape/axes."""
+    tensor = numpy_helper.from_array(np.array(vals, dtype=np.int64), name=name)
+    return tensor
+
+
+class ONNXBuilder:
+    def __init__(self, model_name):
+        self.model_name = model_name
+        self.nodes = []
+        self.initializers = []
+        self.name_counter = [0]
+        # Maps MXNet node name -> ONNX tensor name
+        self.name_map = {}
+        self.eps = 1e-5
+
+    def new_name(self, base):
+        self.name_counter[0] += 1
+        return f'{base}_{self.name_counter[0]}'
+
+    def resolve(self, mxnet_ref):
+        """
+        Args:
+            mxnet_ref is either a node index (int) or a node name (str).
+
+        Return ONNX tensor name for an MXNet output, or None.
+        """
+        if isinstance(mxnet_ref, int):
+            # Look up node name by index
+            if 0 <= mxnet_ref < len(self.nodes_json):
+                mxnet_ref = self.nodes_json[mxnet_ref]['name']
+            else:
+                return None
+        return self.name_map.get(mxnet_ref)
+
+    def make_conv(self, node, arg_params):
+        attrs = node['attrs']
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        # Weight is always input[1] (a param node)
+        w_node_idx = node['inputs'][1][0]
+        w_name = self.nodes_json[w_node_idx]['name']
+        weight = arg_params[w_name]
+        w_tensor = self.new_name(w_name)
+        self.initializers.append(ndarr(weight.asnumpy()))
+        # Note: ndarr above loses name; rebuild with name
+        self.initializers[-1] = numpy_helper.from_array(weight.asnumpy(), name=w_tensor)
+
+        kernel = parse_tuple(attrs['kernel'])
+        stride = parse_tuple(attrs['stride'])
+        pad = parse_tuple(attrs['pad'])
+        dilate = parse_tuple(attrs['dilate'])
+        groups = int(attrs['num_group'])
+
+        out = self.new_name(name)
+        # ONNX pads: [top, left, bottom, right] = [ph, pw, ph, pw]
+        pads = [pad[0], pad[1], pad[0], pad[1]] if len(pad) == 2 else list(pad) * 2
+        conv = helper.make_node(
+            'Conv', [mx_in, w_tensor], [out],
+            name=name,
+            kernel_shape=list(kernel),
+            strides=list(stride),
+            pads=pads,
+            dilations=list(dilate),
+            group=groups,
+        )
+        self.nodes.append(conv)
+        self.name_map[name] = out
+        return True
+
+    def make_batchnorm(self, node, arg_params, aux_params):
+        attrs = node['attrs']
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        eps = float(attrs['eps'])
+
+        gamma_name = self.nodes_json[node['inputs'][1][0]]['name']
+        beta_name = self.nodes_json[node['inputs'][2][0]]['name']
+        mean_name = self.nodes_json[node['inputs'][3][0]]['name']
+        var_name = self.nodes_json[node['inputs'][4][0]]['name']
+
+        gamma_t = self.new_name(gamma_name)
+        beta_t = self.new_name(beta_name)
+        mean_t = self.new_name(mean_name)
+        var_t = self.new_name(var_name)
+        for t, key in [(gamma_t, gamma_name), (beta_t, beta_name),
+                       (mean_t, mean_name), (var_t, var_name)]:
+            src = arg_params.get(key)
+            if src is None:
+                src = aux_params.get(key)
+            self.initializers.append(numpy_helper.from_array(src.asnumpy().astype(np.float32), name=t))
+
+        out = self.new_name(name)
+        bn = helper.make_node(
+            'BatchNormalization',
+            [mx_in, gamma_t, beta_t, mean_t, var_t], [out],
+            name=name, epsilon=eps,
+        )
+        self.nodes.append(bn)
+        self.name_map[name] = out
+        return True
+
+    def make_relu(self, node):
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        out = self.new_name(name)
+        relu = helper.make_node('Relu', [mx_in], [out], name=name)
+        self.nodes.append(relu)
+        self.name_map[name] = out
+        return True
+
+    def make_concat(self, node):
+        name = node['name']
+        axis = int(node['attrs']['dim'])
+        mx_inputs = [self.resolve(i[0]) for i in node['inputs']]
+        if any(x is None for x in mx_inputs):
+            return False
+        out = self.new_name(name)
+        concat = helper.make_node('Concat', mx_inputs, [out], name=name, axis=axis)
+        self.nodes.append(concat)
+        self.name_map[name] = out
+        return True
+
+    def make_pooling(self, node):
+        attrs = node['attrs']
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        pool_type = attrs['pool_type']
+        kernel = parse_tuple(attrs['kernel'])
+        stride = parse_tuple(attrs['stride'])
+        pad = parse_tuple(attrs['pad'])
+
+        out = self.new_name(name)
+        pads = [pad[0], pad[1], pad[0], pad[1]] if len(pad) == 2 else list(pad) * 2
+        if pool_type == 'max':
+            pool = helper.make_node(
+                'MaxPool', [mx_in], [out], name=name,
+                kernel_shape=list(kernel), strides=list(stride), pads=pads,
+            )
+        elif pool_type == 'avg':
+            pool = helper.make_node(
+                'AveragePool', [mx_in], [out], name=name,
+                kernel_shape=list(kernel), strides=list(stride), pads=pads,
+            )
+        else:
+            raise ValueError(f'Unknown pool_type: {pool_type}')
+        self.nodes.append(pool)
+        self.name_map[name] = out
+        return True
+
+    def make_reshape(self, node):
+        name = node['name']
+        shape_str = node['attrs']['shape']
+        shape = parse_tuple(shape_str)
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+
+        # Convert MXNet shape notation to ONNX-compatible
+        # -2, -3, -4 (relative dims) are not supported by ONNX; handled by caller
+        onnx_shape = []
+        for s in shape:
+            if s >= 0 or s == -1:
+                onnx_shape.append(s)
+            else:
+                # Unsupported relative dim — caller should have rewritten these
+                raise ValueError(f'Unsupported shape value {s} in {name}')
+
+        out = self.new_name(name)
+        shape_t = self.new_name(f'{name}_shape')
+        self.initializers.append(shape_init(shape_t, onnx_shape))
+        reshape = helper.make_node('Reshape', [mx_in, shape_t], [out], name=name)
+        self.nodes.append(reshape)
+        self.name_map[name] = out
+        return True
+
+    def make_unsqueeze(self, node):
+        name = node['name']
+        axis = int(node['attrs']['axis'])
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        out = self.new_name(name)
+        axes_t = self.new_name(f'{name}_axes')
+        self.initializers.append(shape_init(axes_t, [axis]))
+        unsq = helper.make_node('Unsqueeze', [mx_in, axes_t], [out], name=name)
+        self.nodes.append(unsq)
+        self.name_map[name] = out
+        return True
+
+    def make_squeeze(self, node):
+        name = node['name']
+        axis = int(node['attrs']['axis'])
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        out = self.new_name(name)
+        axes_t = self.new_name(f'{name}_axes')
+        self.initializers.append(shape_init(axes_t, [axis]))
+        sq = helper.make_node('Squeeze', [mx_in, axes_t], [out], name=name)
+        self.nodes.append(sq)
+        self.name_map[name] = out
+        return True
+
+    def make_transpose(self, node):
+        name = node['name']
+        perm = parse_tuple(node['attrs']['axes'])
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        out = self.new_name(name)
+        tr = helper.make_node('Transpose', [mx_in], [out], name=name, perm=list(perm))
+        self.nodes.append(tr)
+        self.name_map[name] = out
+        return True
+
+    def make_dropout(self, node):
+        # Inference: identity
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        self.name_map[name] = mx_in
+        return True
+
+    def make_gemm(self, node, arg_params):
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])
+        if mx_in is None:
+            return False
+        w_node_idx = node['inputs'][1][0]
+        w_name = self.nodes_json[w_node_idx]['name']
+        b_node_idx = node['inputs'][2][0]
+        b_name = self.nodes_json[b_node_idx]['name']
+
+        w_t = self.new_name(w_name)
+        b_t = self.new_name(b_name)
+        self.initializers.append(numpy_helper.from_array(arg_params[w_name].asnumpy().astype(np.float32), name=w_t))
+        self.initializers.append(numpy_helper.from_array(arg_params[b_name].asnumpy().astype(np.float32), name=b_t))
+
+        out = self.new_name(name)
+        # Y = X @ W^T + b  (transB=1)
+        gemm = helper.make_node('Gemm', [mx_in, w_t, b_t], [out], name=name, transB=1, alpha=1.0, beta=1.0)
+        self.nodes.append(gemm)
+        self.name_map[name] = out
+        return True
+
+    def build(self, sym_dict, arg_params, aux_params, seq_len, hidden_dim, img_width):
+        self.nodes_json = sym_dict['nodes']
+        node_map = {node['name']: node for node in self.nodes_json}
+
+        # Find input node (data)
+        data_node = self.nodes_json[0]
+        # Dynamic width: batch and width are free dimensions
+        graph_input = helper.make_tensor_value_info('data', FLOAT, [None, 1, 32, None])
+        self.name_map['data'] = 'data'
+
+        # Walk nodes in order, handling each op
+        for idx, node in enumerate(self.nodes_json):
+            op = node.get('op', 'null')
+            name = node.get('name', '')
+
+            if op == 'null':
+                # Parameter node (weight/data) — no-op
+                continue
+            if op == '_zeros':
+                # Initial hidden state for RNN — handled in GRU section
+                continue
+            # Skip MXNet nodes that we replace with a dynamic-width-friendly
+            # equivalent. The MXNet reshape(0,-3,0) + expand_dims + squeeze +
+            # transpose chain has different 0-index semantics than ONNX and
+            # doesn't support dynamic width.
+            if name in ('densenet0_reshape0', 'densenet0_expand_dims0',
+                        'dropout0_fwd', 'crnn0_squeeze0', 'crnn0_transpose0'):
+                if name == 'densenet0_reshape0':
+                    self.make_post_densenet(node)
+                continue
+            if op == 'Reshape':
+                # For GRU param reshapes (gru0_reshape*), skip — they're for
+                # MXNet's internal RNN param packing which we bypass.
+                if name.startswith('gru0_reshape'):
+                    continue
+                # For reshape0 (the final reshape before FC): (-3, -2) -> (-1, hidden_dim)
+                if name == 'reshape0':
+                    mx_in = self.resolve(node['inputs'][0][0])
+                    out = self.new_name(name)
+                    shape_t = self.new_name(f'{name}_shape')
+                    self.initializers.append(shape_init(shape_t, [-1, hidden_dim]))
+                    self.nodes.append(helper.make_node('Reshape', [mx_in, shape_t], [out], name=name))
+                    self.name_map[name] = out
+                    continue
+                self.make_reshape(node)
+            elif op == 'Convolution':
+                self.make_conv(node, arg_params)
+            elif op == 'BatchNorm':
+                self.make_batchnorm(node, arg_params, aux_params)
+            elif op == 'Activation':
+                self.make_relu(node)
+            elif op == 'Concat':
+                self.make_concat(node)
+            elif op == 'Pooling':
+                self.make_pooling(node)
+            elif op == 'expand_dims':
+                self.make_unsqueeze(node)
+            elif op == 'squeeze':
+                self.make_squeeze(node)
+            elif op == 'transpose':
+                self.make_transpose(node)
+            elif op == 'Dropout':
+                self.make_dropout(node)
+            elif op == 'FullyConnected':
+                self.make_gemm(node, arg_params)
+            elif op == '_rnn_param_concat':
+                # Bypassed — GRU built from raw params in make_gru()
+                continue
+            elif op == 'RNN':
+                self.make_gru(node, arg_params)
+            else:
+                print(f'  WARNING: unhandled op {op} ({name})')
+
+        # Find the pred_fc output tensor name
+        pred_fc_node = node_map['pred_fc']
+        pred_fc_out = self.name_map.get('pred_fc')
+
+        # Add softmax
+        softmax_out = 'softmax_output'
+        sm = helper.make_node('Softmax', [pred_fc_out], [softmax_out], name='softmax', axis=-1)
+        self.nodes.append(sm)
+
+        graph_output = helper.make_tensor_value_info(softmax_out, FLOAT, [None, None])
+
+        graph = helper.make_graph(
+            self.nodes,
+            f'{self.model_name}_graph',
+            [graph_input],
+            [graph_output],
+            initializer=self.initializers,
+        )
+        model = helper.make_model(graph, opset_imports=[helper.make_opsetid('', OPSET)])
+        model.ir_version = 7
+        return model
+
+    def make_post_densenet(self, node):
+        """
+        Replace MXNet's reshape+expand_dims+dropout+squeeze+transpose chain
+        with a dynamic-width-friendly equivalent.
+
+        MXNet DenseNet output: (batch, 256, 2, seq)  where seq = W/4
+        Target GRU input:      (seq, batch, 512)
+
+        Sequence:
+          1. transpose (0, 3, 1, 2): (batch, seq, 256, 2)
+          2. reshape   (0, 0, -1):   (batch, seq, 512)   [flatten 256*2]
+          3. transpose (1, 0, 2):    (seq, batch, 512)
+        """
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])  # DenseNet pool output
+        if mx_in is None:
+            return False
+
+        # 1. transpose (batch, 256, 2, seq) -> (batch, seq, 256, 2)
+        t1 = self.new_name(f'{name}_t1')
+        self.nodes.append(helper.make_node('Transpose', [mx_in], [t1],
+                                           name=f'{name}_t1', perm=[0, 3, 1, 2]))
+
+        # 2. reshape (batch, seq, 256*2=512)
+        t2 = self.new_name(f'{name}_t2')
+        shape_t = self.new_name(f'{name}_shape')
+        self.initializers.append(shape_init(shape_t, [0, 0, -1]))
+        self.nodes.append(helper.make_node('Reshape', [t1, shape_t], [t2],
+                                           name=f'{name}_t2'))
+
+        # 3. transpose (seq, batch, 512) — the GRU input layout
+        t3 = self.new_name(f'{name}_t3')
+        self.nodes.append(helper.make_node('Transpose', [t2], [t3],
+                                           name=f'{name}_t3', perm=[1, 0, 2]))
+
+        # Store as crnn0_transpose0 output so the RNN node can consume it
+        self.name_map['crnn0_transpose0'] = t3
+        return True
+
+    def make_gru(self, node, arg_params):
+        """
+        Build ONNX bidirectional GRU from raw forward/backward params.
+
+        MXNet RNN op consumes (data, params_concat, initial_h).
+        Bypass the internal param packing and build ONNX GRU directly:
+          X: (seq_len, batch, 512)
+          W: (2, 384, 512)  [fwd_i2h, bwd_i2h]
+          R: (2, 384, 128)  [fwd_h2h, bwd_h2h]
+          B: (2, 768)       [fwd[i2h_bias,h2h_bias], bwd[...]]
+          direction=bidirectional, linear_before_reset=0
+        """
+        name = node['name']
+        mx_in = self.resolve(node['inputs'][0][0])  # transposed DenseNet output
+        if mx_in is None:
+            return False
+
+        # Derive GRU dims from actual params (architecture is densenet-lite-gru)
+        i2h0 = arg_params['gru0_l0_i2h_weight'].asnumpy()
+        hidden = i2h0.shape[0] // 3  # 3*hidden, hidden = 128
+        input_size = i2h0.shape[1]
+        # MXNet GRU gate order is [r, z, h]; ONNX GRU expects [z, r, h].
+        # Empirical finding: reorder (0<->1) + linear_before_reset=1 matches MXNet.
+        idx = np.array([1, 0, 2])
+
+        def reorder_gates(mat):
+            # mat shape (3*hidden, ...) or (3*hidden,)
+            if mat.ndim == 1:
+                return mat.reshape(3, hidden)[idx].reshape(-1)
+            else:
+                return mat.reshape(3, hidden, -1)[idx].reshape(-1, mat.shape[-1])
+
+        # Collect forward/backward GRU params
+        fwd_i2h = reorder_gates(arg_params['gru0_l0_i2h_weight'].asnumpy())  # (384, 512)
+        fwd_h2h = reorder_gates(arg_params['gru0_l0_h2h_weight'].asnumpy())  # (384, 128)
+        fwd_i2h_b = reorder_gates(arg_params['gru0_l0_i2h_bias'].asnumpy())  # (384,)
+        fwd_h2h_b = reorder_gates(arg_params['gru0_l0_h2h_bias'].asnumpy())  # (384,)
+        bwd_i2h = reorder_gates(arg_params['gru0_r0_i2h_weight'].asnumpy())
+        bwd_h2h = reorder_gates(arg_params['gru0_r0_h2h_weight'].asnumpy())
+        bwd_i2h_b = reorder_gates(arg_params['gru0_r0_i2h_bias'].asnumpy())
+        bwd_h2h_b = reorder_gates(arg_params['gru0_r0_h2h_bias'].asnumpy())
+
+        # ONNX GRU weights: W (2, 3h, input), R (2, 3h, h), B (2, 6h)
+        W = np.stack([fwd_i2h, bwd_i2h]).astype(np.float32)  # (2, 384, 512)
+        R = np.stack([fwd_h2h, bwd_h2h]).astype(np.float32)  # (2, 384, 128)
+        B = np.stack([np.concatenate([fwd_i2h_b, fwd_h2h_b]),
+                      np.concatenate([bwd_i2h_b, bwd_h2h_b])]).astype(np.float32)  # (2, 768)
+
+        w_t = self.new_name('gru_W')
+        r_t = self.new_name('gru_R')
+        b_t = self.new_name('gru_B')
+        self.initializers.append(numpy_helper.from_array(W, name=w_t))
+        self.initializers.append(numpy_helper.from_array(R, name=r_t))
+        self.initializers.append(numpy_helper.from_array(B, name=b_t))
+
+        # GRU output Y: (seq_len, num_directions, batch, hidden)
+        y_t = self.new_name('gru_Y')
+        gru = helper.make_node(
+            'GRU', [mx_in, w_t, r_t, b_t], [y_t],
+            name=name,
+            hidden_size=hidden,
+            direction='bidirectional',
+            linear_before_reset=1,
+        )
+        self.nodes.append(gru)
+
+        # Transform Y (seq_len, 2, batch, 128) -> (seq_len, batch, 2, 128) -> (seq_len, batch, 256)
+        y_tr_t = self.new_name('gru_Y_tr')
+        self.nodes.append(helper.make_node('Transpose', [y_t], [y_tr_t], name='gru_Y_tr', perm=[0, 2, 1, 3]))
+        y_rs_t = self.new_name('gru_Y_rs')
+        shape_t = self.new_name('gru_Y_shape')
+        self.initializers.append(shape_init(shape_t, [0, 0, -1]))
+        self.nodes.append(helper.make_node('Reshape', [y_tr_t, shape_t], [y_rs_t], name='gru_Y_reshape'))
+
+        # Store result for the final reshape0 (which expects (seq_len, batch, 256))
+        self.name_map['gru0_rnn0'] = y_rs_t
+        return True
+
+
+def convert(model_info):
+    name = model_info['name']
+    model_dir = model_info['dir']
+    prefix_path = os.path.join(model_dir, model_info['prefix'])
+    epoch = model_info['epoch']
+    img_width = model_info['img_width']
+
+    seq_len = img_width // 4
+    hidden_dim = model_info['hidden'] * 2
+
+    print(f"\n{'='*60}")
+    print(f"Building ONNX model: {name}")
+
+    sym, arg_params, aux_params = mx.model.load_checkpoint(prefix_path, epoch)
+    print(f"  Loaded MXNet checkpoint (epoch {epoch})")
+
+    pred_fc = sym.get_internals()['pred_fc_output']
+    sym_dict = json.loads(pred_fc.tojson())
+
+    builder = ONNXBuilder(name)
+    model = builder.build(sym_dict, arg_params, aux_params, seq_len, hidden_dim, img_width)
+
+    output_path = os.path.join(model_dir, 'model.onnx')
+    onnx.save(model, output_path)
+    size_kb = os.path.getsize(output_path) / 1024
+    print(f"  SAVED: {output_path} ({size_kb:.1f} KB)")
+
+    # Verify
+    try:
+        onnx.checker.check_model(model)
+        print(f"  ONNX structural check: PASSED")
+    except Exception as e:
+        print(f"  ONNX structural check: FAILED - {e}")
+
+    # Print graph summary
+    ops = {}
+    for n in model.graph.node:
+        ops[n.op_type] = ops.get(n.op_type, 0) + 1
+    print(f"  Ops ({len(ops)} types): {dict(sorted(ops.items()))}")
+    return output_path
+
+
+if __name__ == '__main__':
+    print("ONNX Model Builder for ALAS cnocr Models")
+    print(f"MXNet: {mx.__version__}, onnx: {onnx.__version__}")
+
+    models = [
+        {
+            'name': 'azur_lane',
+            'dir': './bin/cnocr_models/azur_lane',
+            'prefix': 'cnocr-v1.2.0-densenet-lite-gru',
+            'epoch': 15,
+            'img_width': 280,
+            'hidden': 128,
+        },
+        {
+            'name': 'azur_lane_jp',
+            'dir': './bin/cnocr_models/azur_lane_jp',
+            'prefix': 'cnocr-v1.2.0-densenet-lite-gru',
+            'epoch': 20,
+            'img_width': 280,
+            'hidden': 128,
+        },
+        {
+            'name': 'cnocr',
+            'dir': './bin/cnocr_models/cnocr',
+            'prefix': 'cnocr-v1.2.0-densenet-lite-gru',
+            'epoch': 39,
+            'img_width': 280,
+            'hidden': 128,
+        },
+        {
+            'name': 'jp',
+            'dir': './bin/cnocr_models/jp',
+            'prefix': 'cnocr-v1.2.0-densenet-lite-gru',
+            'epoch': 125,
+            'img_width': 280,
+            'hidden': 128,
+        },
+        {
+            'name': 'tw',
+            'dir': './bin/cnocr_models/tw',
+            'prefix': 'cnocr-v1.2.0-densenet-lite-gru',
+            'epoch': 63,
+            'img_width': 280,
+            'hidden': 128,
+        },
+    ]
+
+    for m in models:
+        convert(m)
+
+    print(f"\nDone.")

module/ocr/al_ocr.py

@@ -176,7 +176,7 @@ class AlOcr(CnOcr):
         prefix = os.path.join(self._model_dir, self._model_file_prefix)
         data_names = ['data']
         data_shapes = [(data_names[0], (hp.batch_size, 1, hp.img_height, hp.img_width))]
-        logger.info('Loading OCR model: %s' % self._model_dir)  # Change log appearance.
+        logger.info('Loading OCR model (MXNET): %s' % self._model_dir)  # Change log appearance.
         mod = load_module(
             prefix,
             self._model_epoch,
@@ -235,3 +235,62 @@ class AlOcr(CnOcr):
         img_list, img_widths = self._pad_arrays(img_list)
         image = cv2.hconcat(img_list)[0, :, :]
         Image.fromarray(image).show()
+
+
+class _OnnxModule:
+    """
+    Thin wrapper that presents the same `predict(sample) -> NDArray`
+    interface as an MXNet Module, so that CnOcr._predict works unchanged.
+    """
+
+    def __init__(self, session):
+        self._session = session
+        self._input_name = session.get_inputs()[0].name
+
+    def predict(self, sample):
+        import mxnet as mx
+
+        if isinstance(sample, mx.nd.NDArray):
+            sample = sample.asnumpy()
+        # sample: (batch, 1, 32, width)  ->  output: (seq_len * batch, num_classes)
+        out = self._session.run(None, {self._input_name: np.asarray(sample, dtype=np.float32)})[0]
+        return mx.nd.array(out)
+
+
+class AlOcrOnnx(AlOcr):
+    """
+    Subclass of AlOcr that runs inference through ONNX Runtime instead of MXNet,
+    providing faster CPU inference with numerically identical output.
+    All pre/post-processing is inherited unchanged.
+
+    Requires onnxruntime installed and model.onnx in the model directory
+    (generated by dev_tools/convert_mxnet_to_onnx.py from the MXNet checkpoint).
+
+    Parameters are identical to AlOcr.
+
+    Enable by UseOcrOnnx in deploy config.
+    """
+
+    def _get_module(self, context):
+        _network, self._hp = gen_network(self._model_name, self._hp, self._net_prefix)
+        onnx_path = os.path.join(self._model_dir, 'model.onnx')
+
+        if not os.path.exists(onnx_path):
+            logger.warning(f'ONNX model not found: {onnx_path}, '
+                           'falling back to MXNet')
+            return AlOcr._get_module(self, context)
+
+        try:
+            import onnxruntime as ort
+        except ImportError:
+            logger.warning('onnxruntime not installed, falling back to MXNet')
+            return AlOcr._get_module(self, context)
+
+        logger.info(f'Loading OCR model (ONNX): {onnx_path}')
+        so = ort.SessionOptions()
+        # intra_op_num_threads=1 avoids thread-scheduling overhead on the small GRU model (hidden=128). 
+        # Using all cores (default) is measurably slower
+        # because the per-op parallelisation gain is outweighed by thread-pool synchronisation cost.
+        so.intra_op_num_threads = 1
+        session = ort.InferenceSession(onnx_path, so, providers=['CPUExecutionProvider'])
+        return _OnnxModule(session)

module/ocr/models.py

@@ -1,65 +1,76 @@
 from module.base.decorator import cached_property
+from module.webui.setting import State
+
+
+def _ocr_class():
+    if not State.deploy_config.UseOcrOnnx:
+        from module.ocr.al_ocr import AlOcr
+        return AlOcr
+    from module.ocr.al_ocr import AlOcrOnnx
+    return AlOcrOnnx
 
 
 class OcrModel:
     @cached_property
     def azur_lane(self):
         # Folder: ./bin/cnocr_models/azur_lane
-        # Size: 3.25MB
+        # Size: 3.25MB (MXNet) / 3.34MB (ONNX)
         # Model: densenet-lite-gru
         # Epoch: 15
         # Validation accuracy: 99.43%
         # Font: Impact, AgencyFB-Regular, MStiffHeiHK-UltraBold
         # Charset: 0123456789ABCDEFGHIJKLMNPQRSTUVWXYZ:/- (Letter 'O' and <space> is not included)
         # _num_classes: 39
-        from module.ocr.al_ocr import AlOcr
+        return _ocr_class()(model_name='densenet-lite-gru', model_epoch=15,
-        return AlOcr(model_name='densenet-lite-gru', model_epoch=15, root='./bin/cnocr_models/azur_lane',
+                            root='./bin/cnocr_models/azur_lane', name='azur_lane')
-                     name='azur_lane')
 
     @cached_property
     def azur_lane_jp(self):
         # Folder: ./bin/cnocr_models/azur_lane_jp
-        # Size: 3.25MB
+        # Size: 3.25MB (MXNet) / 3.34MB (ONNX)
         # Model: densenet-lite-gru
         # Epoch: 20
         # Validation accuracy: 99.01%
         # Font: Impact, VibeMO Compressed Pro Thin, Folk R, Source Han Serif JP
         # Charset: 0123456789ABCDEFGHIJKLMNPQRSTUVWXYZ:/- (Letter 'O' and <space> is not included)
         # _num_classes: 39
-        from module.ocr.al_ocr import AlOcr
+        return _ocr_class()(model_name='densenet-lite-gru', model_epoch=20,
-        return AlOcr(model_name='densenet-lite-gru', model_epoch=20, root='./bin/cnocr_models/azur_lane_jp',
+                            root='./bin/cnocr_models/azur_lane_jp', name='azur_lane_jp')
-                     name='azur_lane_jp')
 
     @cached_property
     def cnocr(self):
         # Folder: ./bin/cnocr_models/cnocr
-        # Size: 9.51MB
+        # Size: 9.51MB (MXNet) / 9.75MB (ONNX)
         # Model: densenet-lite-gru
         # Epoch: 39
         # Validation accuracy: 99.04%
         # Font: Various
         # Charset: Number, English character, Chinese character, symbols, <space>
         # _num_classes: 6426
-        from module.ocr.al_ocr import AlOcr
+        return _ocr_class()(model_name='densenet-lite-gru', model_epoch=39,
-        return AlOcr(model_name='densenet-lite-gru', model_epoch=39, root='./bin/cnocr_models/cnocr', name='cnocr')
+                            root='./bin/cnocr_models/cnocr', name='cnocr')
 
     @cached_property
     def jp(self):
-        from module.ocr.al_ocr import AlOcr
+        # Folder: ./bin/cnocr_models/jp
-        return AlOcr(model_name='densenet-lite-gru', model_epoch=125, root='./bin/cnocr_models/jp', name='jp')
+        # Size: 6.36MB (ONNX)
+        # Model: densenet-lite-gru
+        # Epoch: 125
+        return _ocr_class()(model_name='densenet-lite-gru', model_epoch=125,
+                            root='./bin/cnocr_models/jp', name='jp')
 
     @cached_property
     def tw(self):
         # Folder: ./bin/cnocr_models/tw
-        # Size: 8.43MB
+        # Size: 8.43MB (MXNet) / 8.64MB (ONNX)
         # Model: densenet-lite-gru
         # Epoch: 63
         # Validation accuracy: 99.24%
         # Font: Various, 6 kinds
         # Charset: Numbers, Upper english characters, Chinese traditional characters
         # _num_classes: 5322
-        from module.ocr.al_ocr import AlOcr
+        return _ocr_class()(model_name='densenet-lite-gru', model_epoch=63,
-        return AlOcr(model_name='densenet-lite-gru', model_epoch=63, root='./bin/cnocr_models/tw', name='tw')
+                            root='./bin/cnocr_models/tw', name='tw')
 
 
 OCR_MODEL = OcrModel()