问题:
我已经训练了卷积神经网络(CNN)来确定/检测给定图像块中是否存在感兴趣的对象。
现在给出一个大图像,我试图通过将我的CNN模型应用到图像中每个像素周围的补丁,以滑动窗口方式定位图像中所有出现的对象。然而,这非常缓慢。
我的测试图像的大小是(512 x 512)。而且,对于我的caffe网,测试批量大小为1024,色块大小为(65 x 65 x 1)。
我尝试在一批补丁(size = test_batch_size)上应用我的caffe网,而不是一次只应用一个补丁。即使这样,它也很慢。
以下是我目前的解决方案,速度很慢。除了对我的测试图像进行下采样以加快速度之外,我将不胜感激。
当前解决方案非常缓慢:
def detectObjects(net, input_file, output_file):
# read input image
inputImage = plt.imread(input_file)
# get test_batch_size and patch_size used for cnn net
test_batch_size = net.blobs['data'].data.shape[0]
patch_size = net.blobs['data'].data.shape[2]
# collect all patches
w = np.int(patch_size / 2)
num_patches = (inputImage.shape[0] - patch_size) * \
(inputImage.shape[1] - patch_size)
patches = np.zeros((patch_size, patch_size, num_patches))
patch_indices = np.zeros((num_patches, 2), dtype='int64')
count = 0
for i in range(w + 1, inputImage.shape[0] - w):
for j in range(w + 1, inputImage.shape[1] - w):
# store patch center index
patch_indices[count, :] = [i, j]
# store patch
patches[:, :, count] = \
inputImage[(i - w):(i + w + 1), (j - w):(j + w + 1)]
count += 1
print "Extracted %s patches" % num_patches
# Classify patches using cnn and write result to output image
outputImage = np.zeros_like(inputImage)
outputImageFlat = np.ravel(outputImage)
pad_w = test_batch_size - num_patches % test_batch_size
patches = np.pad(patches, ((0, 0), (0, 0), (0, pad_w)),
'constant')
patch_indices = np.pad(patch_indices, ((0, pad_w), (0, 0)),
'constant')
start_time = time.time()
for i in range(0, num_patches, test_batch_size):
# get current batch of patches
cur_pind = patch_indices[i:i + test_batch_size, :]
cur_patches = patches[:, :, i:i + test_batch_size]
cur_patches = np.expand_dims(cur_patches, 0)
cur_patches = np.rollaxis(cur_patches, 3)
# apply cnn on current batch of images
net.blobs['data'].data[...] = cur_patches
output = net.forward()
prob_obj = output['prob'][:, 1]
if i + test_batch_size > num_patches:
# remove padded part
num_valid = num_patches - i
prob_obj = prob_obj[0:num_valid]
cur_pind = cur_pind[0:num_valid, :]
# set output
cur_pind_lin = np.ravel_multi_index((cur_pind[:, 0],
cur_pind[:, 1]),
outputImage.shape)
outputImageFlat[cur_pind_lin] = prob_obj
end_time = time.time()
print 'Took %s seconds' % (end_time - start_time)
# Save output
skimage.io.imsave(output_file, outputImage * 255.0)
我希望用线条
net.blobs['data'].data[...] = cur_patches
output = net.forward()
caffe会使用GPU并行地对cur_patches中的所有补丁进行分类。不知道为什么它仍然很慢。
答案 0 :(得分:1)
我认为您所寻找的内容在Casting a Classifier into a Fully Convolutional Network of the "net surgery" tutorial部分中有描述
这个解决方案基本上说的是,"InnerProduct"
层可以转换为等效转换层,而不是转换层后跟"InnerProduct"
层进行分类。 strong>完全卷积网络,可以处理任何大小的图像并根据输入大小输出预测
转向完全卷积式架构将大大减少您当前进行的重新计算的数量,并且应该显着加快您的流程。
加速的另一个可能方向是使用truncated SVD trick通过两个较低等级矩阵的乘积来近似高维"InnerProduct"
层。