Color Space Conversion¶
This example showcases different color space conversion operations available in DALI.
Defining the pipeline¶
[1]:
from __future__ import division
import nvidia.dali.ops as ops
import nvidia.dali.types as types
from nvidia.dali.pipeline import Pipeline
image_dir = "images"
class SimplePipeline(Pipeline):
def __init__(self, batch_size, num_threads, device_id):
super(SimplePipeline, self).__init__(batch_size, num_threads, device_id, seed = 12)
self.input = ops.FileReader(file_root = image_dir)
self.decode = ops.HostDecoder(output_type = types.RGB)
self.copy = ops.Copy(device = 'gpu')
def add_color_space_conversion(conversions, name, input_type, output_type):
conversions['cpu'][name] = ops.ColorSpaceConversion(device = 'cpu', image_type = input_type, output_type = output_type)
conversions['gpu'][name] = ops.ColorSpaceConversion(device = 'gpu', image_type = input_type, output_type = output_type)
self.conversions = { 'cpu': {}, 'gpu': {} }
add_color_space_conversion(self.conversions, 'rgb2bgr', types.RGB, types.BGR )
add_color_space_conversion(self.conversions, 'rgb2ycbcr', types.RGB, types.YCbCr )
add_color_space_conversion(self.conversions, 'rgb2gray', types.RGB, types.GRAY )
def define_graph(self):
self.jpegs, self.labels = self.input()
images = self.decode(self.jpegs)
images_gpu = images.gpu()
outputs = [images]
for device in ['cpu', 'gpu']:
conv_list = list(self.conversions[device].values())
n = len(conv_list)
out = [images_gpu if device == 'gpu' else images for _ in range(n)]
for i in range(n):
out[i] = conv_list[i](out[i])
outputs = outputs + out
return outputs
def iter_setup(self):
pass
Building and running the pipeline¶
[2]:
batch_size = 32
pipe = SimplePipeline(batch_size=batch_size, num_threads=2, device_id = 0)
pipe.build()
pipe_out = pipe.run()
Visualizing the results¶
[3]:
import matplotlib.pyplot as plt
import math
from synsets import imagenet_synsets
import matplotlib.gridspec as gridspec
n = 1
len_outputs = len(pipe_out)
original_images = pipe_out[0]
n_conversions = (len_outputs - 1) // 2
conversions_cpu = [elem for elem in pipe_out[1:n_conversions+1]]
conversions_gpu = [elem for elem in pipe_out[n_conversions+1:]]
titles = list(pipe.conversions['cpu']) # gpu is the same
def show_images(original, conversions, titles_conversions, device):
outputs = conversions
titles = [elem + " " + device for elem in titles_conversions]
len_outputs = len(outputs)
fig = plt.figure(figsize = (16,16))
columns = 4
rows = 1 + int(math.ceil(1.*len_outputs / columns))
gs = gridspec.GridSpec(rows, columns)
plt.subplot(gs[0])
plt.axis("off")
plt.title("original")
plt.imshow(original.at(n))
for i in range(len_outputs):
plt.subplot(gs[i+1])
plt.axis("off")
plt.title(titles[i])
img_chw = outputs[i].as_cpu().at(n) if device == 'gpu' else outputs[i].at(n)
shape = img_chw.shape
if shape[2] == 1:
plt.imshow(img_chw.reshape(shape[0], shape[1]), cmap='gray')
else:
plt.imshow(img_chw)
show_images(original=original_images, conversions=conversions_cpu, titles_conversions=titles, device='cpu')
show_images(original=original_images, conversions=conversions_gpu, titles_conversions=titles, device='gpu')