矩形图

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111)
#rectange3个参数，起点坐标，矩形宽度，矩形高度
rect = plt.Rectangle((0.1,0.1),0.5,0.3)
ax.add_patch(rect)
plt.show()

import matplotlib.pyplot as plt
fig = plt.figure()         #创建图
ax = fig.add_subplot(111)  #创建子图
plt.gca().add_patch(plt.Rectangle((0.1,0.1),0.5,0.3))
plt.show()

#roi框是在图像中画出来的，而图像的原点在左上角，但坐标轴的原点在左下角，所以即使Rectangle中参数一模一样，但在图像和坐标轴中画出来的不一样
def _vis_minibatch(im_blob, rois_blob, labels_blob, overlaps):
    """Visualize a mini-batch for debugging."""
    import matplotlib.pyplot as plt
    #print im_blob
    count = 0
    for i in xrange(rois_blob.shape[0]):
        count += 1
        rois = rois_blob[i, :]
        print(rois)
        im_ind = rois[0]
        roi = rois[1:]
        im = im_blob[im_ind, :, :, :].transpose((1, 2, 0)).copy()
        im += cfg.PIXEL_MEANS
        im = im[:, :, (2, 1, 0)]
        im = im.astype(np.uint8)
        cls = labels_blob[i]
        plt.imshow(im)
        #print 'class: ', cls, ' overlap: ', overlaps[i]
        #print count
        plt.gca().add_patch(
            plt.Rectangle((roi[0], roi[1]), roi[2] - roi[0],
                          roi[3] - roi[1], fill=False,
                          edgecolor='r', linewidth=3)
            )
        plt.show()