redpil 0.2.0

Join the wonderland of python, and decode all your images in a numpy compatible way

redpil

Join the wonderland of python, and decode all your images in a numpy compatible way.

Pillow is a great library for image manipulation. However, many operations fall outside what Pillow can do. As such, many scientific applications require the image to be available as a numpy array. imageio has created an efficient bridge between numpy and Pillow (see benchmarks below).

For large images, having to understand the details of both Pillow and numpy is a serious bottleneck. The goal of the library it to read and write images in a manner natural to numpy users. Images are presented as the values they hold (not indices in a color table) allowing for direct data analysis.

To avoid the need for an other C dependency, this library aims at creating a pure python image decoder for many of the image formats supported by Pillow that depends on other popular libraries such as numpy and scipy to do the heavy lifting in terms of computation. We start with the simple BMP file format. The pure python nature of this library means that we can quickly try to implement encoding and decoding into different image formats.

Bitmap images

Generally, this library will not load memory in a C-contiguous array. Rather the memory order will mostly match what was saved on disk.

Bitmap images will be stored in an order similar to how they arranged in RAM.

Supported file formats

Reading BMP is almost fully supported. Writing is still limited.

• BMP: 1, 4, or 8bit per pixel. Wikipedia

Future file formats

• BMP: more coverage
• JPEG, JPEG2000
• GIF
• PNG
• SVG
• TIFF

Benchmarks

I don't have a fancy benchmarking service like scikit-image or dask has, but here are the benchmarks results compared to a PIL backend. This is running on my SSD, a Samsung 960 Pro which claims it can write at 1.8GB/s. This is pretty close to what redpil achieves.

8 bit BMP grayscale images

Saving images:

================ ============ ============ ============
--                                mode                 
---------------- --------------------------------------
     shape          redpil       pillow      imageio   
================ ============ ============ ============
   (128, 128)      93.4±1μs     254±30μs     369±20μs  
  (1024, 1024)     720±30μs     936±50μs    1.60±0.3ms
  (2048, 4096)    5.25±0.7ms   5.20±0.1ms    10.4±2ms  
 (32768, 32768)    480±10ms     489±5ms     1.34±0.09s
================ ============ ============ ============

Reading image

================ ============= ============ =============
--                                 mode                  
---------------- ----------------------------------------
     shape           redpil       pillow       imageio   
================ ============= ============ =============
   (128, 128)       131±5μs      293±10μs      130±2μs   
  (1024, 1024)      194±10μs    1.03±0.1ms     192±5μs   
  (2048, 4096)    1.69±0.05ms    8.55±1ms    1.67±0.03ms
 (32768, 32768)     350±3ms      230±5μs       354±10ms  
================ ============= ============ =============

Note, Pillow refuses to read the 1GB image because it thinks it is a fork bomb.

Patched up imageio

As it can be seen, the team at imageio/scikit-image are much better at reading the pillow documentation and understanding how to use it effectively. Their reading speeds actually match the reading speeds of redpil, even though they use pillow as a backend. They even handle what pillow thinks is a forkbomb.

Through writing this module, two bugs were found in imageio that affect the speed of saving images imageio PR #398, and how images were being read imageio PR #399

With PR 398, the saving speed of imageio+pillow now matches that of redpil. Note I'm always using the computer when running benchmarks, so take the exact numbers with a grain of salt.

Saving

================ ============ ============ ============
--                                mode                 
---------------- --------------------------------------
     shape          redpil       pillow      imageio   
================ ============ ============ ============
   (128, 128)      98.3±4μs     245±7μs      350±4μs   
  (1024, 1024)     714±20μs     921±30μs     997±20μs  
  (2048, 4096)    4.83±0.3ms   5.30±0.4ms   5.26±0.2ms
 (32768, 32768)    520±40ms     516±30ms     489±9ms   
================ ============ ============ ============

Reading

================ ============= ============ =============
--                                 mode                  
---------------- ----------------------------------------
     shape           redpil       pillow       imageio   
================ ============= ============ =============
   (128, 128)      129±0.7μs     284±2μs      129±0.7μs  
  (1024, 1024)      191±2μs     1.12±0.1ms    190±0.9μs  
  (2048, 4096)    1.62±0.03ms    8.88±1ms    1.63±0.02ms
 (32768, 32768)     357±9ms      223±4μs       361±8ms   
================ ============= ============ =============

History

0.0.1 (2018-09-22)

• First release on PyPI.