python真实mask标签图像和预测的分割mask图像的AP计算
时间: 2023-09-15 13:17:32 浏览: 161
基于pytorch中的torchvision实现的一个maskrcnn的目标检测和实例分割
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要计算真实mask标签图像和预测的分割mask图像的AP,可以使用Python中的一些库和函数来实现。以下是一个简单的实现过程:
1. 首先,将预测的分割mask图像和真实的mask标签图像转换成二进制数组,其中1表示正样本(像素属于目标),0表示负样本(像素不属于目标)。
```python
import numpy as np
# 将预测的分割mask图像转换成二进制数组
pred_mask = np.array(pred_mask > threshold, dtype=np.int)
# 将真实的mask标签图像转换成二进制数组
true_mask = np.array(true_mask > 0, dtype=np.int)
```
其中,threshold是一个阈值,用于将预测的概率值转换成二进制数组。
2. 计算每个类别的IoU(Intersection over Union)。
```python
def iou(true_mask, pred_mask):
intersection = np.logical_and(true_mask, pred_mask)
union = np.logical_or(true_mask, pred_mask)
iou_score = np.sum(intersection) / np.sum(union)
return iou_score
iou_scores = []
for class_id in range(num_classes):
class_true_mask = true_mask == class_id
class_pred_mask = pred_mask == class_id
class_iou = iou(class_true_mask, class_pred_mask)
iou_scores.append(class_iou)
```
其中,num_classes是类别的数量。
3. 根据IoU值和预设的阈值计算TP、FP和FN。
```python
def precision_recall(true_mask, pred_mask, iou_threshold):
intersection = np.logical_and(true_mask, pred_mask)
union = np.logical_or(true_mask, pred_mask)
iou_score = np.sum(intersection) / np.sum(union)
if iou_score > iou_threshold:
tp = 1
fp = 0
fn = 0
else:
tp = 0
fp = 1
fn = 1
return tp, fp, fn
tp_list = []
fp_list = []
fn_list = []
for class_id in range(num_classes):
class_true_mask = true_mask == class_id
class_pred_mask = pred_mask == class_id
class_tp, class_fp, class_fn = precision_recall(class_true_mask, class_pred_mask, iou_threshold)
tp_list.append(class_tp)
fp_list.append(class_fp)
fn_list.append(class_fn)
```
其中,iou_threshold是IoU的阈值。
4. 计算每个类别的精确率(Precision)和召回率(Recall)。
```python
precision_list = []
recall_list = []
for class_id in range(num_classes):
tp = tp_list[class_id]
fp = fp_list[class_id]
fn = fn_list[class_id]
precision = tp / (tp + fp)
recall = tp / (tp + fn)
precision_list.append(precision)
recall_list.append(recall)
```
5. 计算每个类别的AP(Average Precision)。
```python
def compute_ap(precision, recall):
num_thresholds = 11
thresholds = np.linspace(0, 1, num_thresholds)
ap = 0
for threshold in thresholds:
# 找到所有精确率大于等于当前阈值的最大召回率
max_recall = np.max(recall[precision >= threshold])
# 计算当前阈值下的查准率
if np.isnan(max_recall):
precision_at_recall = 0
else:
precision_at_recall = np.max(precision[recall >= max_recall])
# 累加AP
ap += precision_at_recall / num_thresholds
return ap
ap_list = []
for class_id in range(num_classes):
precision = np.array(precision_list[class_id])
recall = np.array(recall_list[class_id])
ap = compute_ap(precision, recall)
ap_list.append(ap)
```
6. 计算mAP(Mean Average Precision)。
```python
mAP = sum(ap_list) / num_classes
```
最终,mAP即为所求的真实mask标签图像和预测的分割mask图像的AP。
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