1. 利用matplotlib.pyplot 畫矩形框
from matplotlib import pyplot as plt
plt.Rectangle( )參數：
plt.Rectangle(self, xy, width, height, angle=0.0, **kwargs)
#可選參數： fill : bool, optional (whether to fill the rect)
edgecolor: mpl color spec; linewidth: float or None
第一個參數是矩形左上角點坐標 tuple (x,y)，第二個參數是矩形寬，第三個參數是矩形高
示例：
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(1,1,1)
rect = plt.Rectangle((0.1,0.1), 0.5, 0.3, fill=False, edgecolor = 'red',linewidth=1)
ax.add_patch(rect)
plt.show()
rect1.jpg
補充，matplotlib中的圖和子圖
在使用pyplot進行繪制圖形時，是對當前的 figure 或者 axes 進行操作，所以需要先取得需要進行操作的子圖，然后利用plt.plot()進行繪圖，默認plt.plot( )會在最近的一個圖上進行繪制
獲得當前的圖： plt.gcf() 獲得當前的子圖: plt.gca()
2. 目標檢測中繪制 bounding boxes
參數 Args：
img: (~numpy.ndarray) in RGB format with shape (3, height, width)
bbox: (~numpy.ndarray) shape in (R, 4), R is the number of bboxes
label: (~numpy.ndarray) An integer array of shape R (R, )
score: (~numpy.ndarray) A float array of shape (R, ), indicating the confidence of predicting
ax: (matplotlib.axes.Axes): visualization is displayed on this axis, if "None", new one
Returns: ~matplotlib.axes.Axes
3. 函數 vis_bbox(img, bbox, label=None, score=None, ax=None) 原始鏈接
def vis_bbox(img, bbox, label=None, score=None, ax=None):
label_names = list(VOC_BBOX_LABEL_NAMES) + ['bg']
# add for index `-1`
if label is not None and not len(bbox) == len(label):
raise ValueError('The length of label must be same as that of bbox')
if score is not None and not len(bbox) == len(score):
raise ValueError('The length of score must be same as that of bbox')
# Returns newly instantiated matplotlib.axes.Axes object if ax is None
ax = vis_image(img, ax=ax)
# If there is no bounding box to display, visualize the image and exit.
if len(bbox) == 0:
return ax
for i, bb in enumerate(bbox):
xy = (bb[1], bb[0])
height = bb[2] - bb[0]
width = bb[3] - bb[1]
ax.add_patch(plot.Rectangle(
xy, width, height, fill=False, edgecolor='red', linewidth=2))
caption = list()
if label is not None and label_names is not None:
lb = label[i]
if not (-1 <= lb < len(label_names)): # modfy here to add backgroud
raise ValueError('No corresponding name is given')
caption.append(label_names[lb])
if score is not None:
sc = score[i]
caption.append('{:.2f}'.format(sc))
if len(caption) > 0:
ax.text(bb[1], bb[0],
': '.join(caption),
style='italic',
bbox={'facecolor': 'white', 'alpha': 0.5, 'pad': 0})
return ax