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scipts/libraries: Update fomo post-processor to use numpy vectors.
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@ -26,8 +26,6 @@
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# OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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import math
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import image
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from ml.utils import NMS
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from micropython import const
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from ulab import numpy as np
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@ -36,38 +34,67 @@ from ulab import numpy as np
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_NO_DETECTION = const(())
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def mod(a, b):
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return a - (b * (a // b))
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def dequantize(model, value):
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if model.output_dtype[0] == 'f':
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return value
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return (value - model.output_zero_point[0]) * model.output_scale[0]
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# FOMO generates an image per class, where each pixel represents the centroid
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# of the trained object. These images are processed with `find_blobs()` to
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# extract centroids, and `get_stats()` is used to get their scores. Overlapping
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# detections are then filtered with NMS and positions are mapped back to the
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# original image, and a list of (rect, score) tuples is returned for each class,
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# representing detected objects.
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class fomo_postprocess:
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def __init__(self, threshold=0.4):
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self.threshold_list = [(math.ceil(threshold * 255), 255)]
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_FOMO_CLASSES = const(1)
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def __init__(self, threshold=0.4, w_scale=1.414214, h_scale=1.414214,
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nms_threshold=0.1, nms_sigma=0.001):
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self.threshold = threshold
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self.w_scale = w_scale
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self.h_scale = h_scale
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self.nms_threshold = nms_threshold
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self.nms_sigma = nms_sigma
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def __call__(self, model, inputs, outputs):
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n, oh, ow, oc = model.output_shape[0]
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nms = NMS(ow, oh, inputs[0].roi)
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for i in range(oc):
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img = image.Image(dequantize(model, outputs[0][0, :, :, i]) * 255)
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blobs = img.find_blobs(
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self.threshold_list, x_stride=1, area_threshold=1, pixels_threshold=1
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)
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for b in blobs:
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rect = b.rect()
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x, y, w, h = rect
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score = (
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img.get_statistics(thresholds=self.threshold_list, roi=rect).l_mean() / 255.0
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)
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nms.add_bounding_box(x, y, x + w, y + h, score, i)
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return nms.get_bounding_boxes()
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ob, oh, ow, oc = model.output_shape[0]
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# Reshape the output to a 2D array
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row_outputs = outputs[0].reshape((oh * ow, oc))
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# Threshold all the scores
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score_indices = np.max(dequantize(model, row_outputs[:, _FOMO_CLASSES:]), axis=1)
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score_indices = np.nonzero(score_indices > self.threshold)[0]
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if not len(score_indices):
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return _NO_DETECTION
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# Get the bounding boxes that have a valid score
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bb = dequantize(model, np.take(row_outputs, score_indices, axis=0))
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# Extract rows and columns
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bb_rows = score_indices // ow
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bb_cols = mod(score_indices, ow)
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# Get the score information
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bb_scores = np.max(bb[:, _FOMO_CLASSES:], axis=1)
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# Get the class information
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bb_classes = np.argmax(bb[:, _FOMO_CLASSES:], axis=1) + _FOMO_CLASSES
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# Scale the bounding boxes to have enough integer precision for NMS
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ib, ih, iw, ic = model.input_shape[0]
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x_center = ((bb_cols + 0.5) / ow) * iw
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y_center = ((bb_rows + 0.5) / oh) * ih
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w_rel = np.full(len(bb_cols), self.w_scale / ow) * iw
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h_rel = np.full(len(bb_rows), self.h_scale / oh) * ih
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nms = NMS(iw, ih, inputs[0].roi)
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for i in range(bb.shape[0]):
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nms.add_bounding_box(x_center[i] - (w_rel[i] / 2),
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y_center[i] - (h_rel[i] / 2),
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x_center[i] + (w_rel[i] / 2),
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y_center[i] + (h_rel[i] / 2),
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bb_scores[i], bb_classes[i])
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return nms.get_bounding_boxes(threshold=self.nms_threshold, sigma=self.nms_sigma)
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# This is a lightweight version of the tiny yolo v2 object detection algorithm.
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@ -100,9 +127,6 @@ class yolo_v2_postprocess:
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def sigmoid(x):
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return 1.0 / (1.0 + np.exp(-x))
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def mod(a, b):
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return a - (b * (a // b))
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def softmax(x):
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e_x = np.exp(x - np.max(x, axis=1, keepdims=True))
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return e_x / np.sum(e_x, axis=1, keepdims=True)
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