imread Documentation Release 0.6 Luis Pedro Coelho

Transcription

1 imread Documentation Release 0.6 Luis Pedro Coelho Sep 27, 2017

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3 Contents 1 Citation INSTALL Bug Reports Indices and tables 9 i

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5 Imread is a very simple libray. It has three functions imread Reads an image from disk imread_multi Reads multiple images from disk (only for file formats that support multiple images) imwrite Save an image to disk That s it. This needs to be used with a a computer vision & image processing packages: mahotas scikit-image OpenCV This grew out of frustration at current image loading solutions in Python, in either my packages [mahotas] or packages from others [scikit-image, for example]. The relationship with numpy is very contained and this could be easily repurposed to load images in other frameworks, even other programming languages. Contents 1

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7 CHAPTER 1 Citation This package is an off-shoot of mahotas. As it, currently, does not have its own publication, so you are asked to cite the mother package: If you use imread-mahotas on a scientific publication, please cite: Luis Pedro Coelho Mahotas: Open source software for scriptable computer vision in Journal of Open Research Software, vol 1, [DOI] In Bibtex author = {Luis Pedro Coelho}, title = {Mahotas: Open source software for scriptable computer vision}, journal = {Journal of Open Research Software}, year = {2013}, doi = { month = {July}, volume = {1} } INSTALL On Windows, you can also just download a pre-built package from C. Gohlke s repository To compile on debian/ubuntu: sudo apt-get install libpng12-dev libtiff4-dev libwebp-dev sudo apt-get install xcftools To compile on Mac: sudo port install libpng tiff webp Either way, you can then install: 3

8 pip install imread Contents: IMREAD This is library to read & write image files. How To Install Mahotas-imread From source You can get the released version using our favorite Python package manager: pip install imread If you prefer, you can download the source from PyPI and run: python setup.py install You will need to have numpy and a C++ compiler. Bleeding Edge (Development) Development happens on github. You can get the development source there. Watch out that these versions are more likely to have problems. On Windows On Windows, Christoph Gohlke does an excelent job maintaining binary packages of imread (and several other packages). conda Imread is not a part of standard conda packages, but on 64 bit Linux, you can get it from this repository < with: conda install -c imread 4 Chapter 1. Citation

9 Formats Supported Format Read Write Since version Notes PNG Y Y 0.1 PNG (16 bits) Y Y 0.4 TIFF Y Y 0.1 JPEG Y Y 0.1 WEBP Y N 0.2 BMP Y N Only uncompressed bitmaps are supported. STK Y N 0.2 LSM Y N XCF Y N Only if xcf2png utility is found in the path. Options Some of the formats allow you to specify options when saving. These are inevitably format specific. PNG png:compression_level Compression level to use, from 0 (no compression) to 9. Setting it to 0 is discouraged. JPEG jpeg:quality An integer determining the quality used by JPEG backend (default is libjpeg default: 75). TIFF tiff:compress Whether to use compression when saving TIFF (default: True) tiff:horizontal-predictor Whether to use horizontal prediction in TIFF. This defaults to True for 16 bit images, and to False for 8 bit images. This is because compressing 16 bit images without horizontal prediction is often counter-productive (see Using imread outside of Python Actually, imread is not a Python library. It s really a C++ library with very good Python/numpy bindings. But you can easily use it from other languages (including C++, of course) by adapting your image representation to the imread interface. The Image and the ImageFactory interfaces You need to support the Image interface: class Image { public: // number of dimensions virtual int ndims() const = 0; // size of dimension d 1.1. INSTALL 5

10 virtual int dim(int d) const = 0; }; // get a pointer to row `r` virtual void* rowp(int r) = 0; It is assumed that an RGB image is represented as H x W x 3 and RGBA as H x W x 4. You also need to support the ImageFactory interface: class ImageFactory { public: Image* create(int nbits, int w, int h, int d); }; The create methods create 2 or 3-dimensional images with nbits per pixel. See the numpy interface in the source code for inspiration. History Version 0.6 ( ) Add supports_format function Make png compression level tunable when calling imsave Add imsave_multi Add partial support for reading PNG files in Gray+alpha format Version ( ) Improve tests to work after installation Fix compilation in MSVC (patch by Christoph Gohlke) Version 0.5 ( ) Add magic-number based format auto-detection Auto detect whether webp is installed Fix WebP reading (update to newer API) Version 0.4 ( ) Add configuration for TIFF saving Correctly save 16 bit PNG images Better error messages for JPEG 6 Chapter 1. Citation

11 Version ( ) Added imload*/imwrite synonyms as suggested by Thouis (Ray) Jones Options framework Allow user to specify JPEG quality when saving Fix loading of 16 bit PNG images Version ( ) Fix possible crash on error with TIFF Fix compilation on Windows (reported by Volker Hilsenstein) Make it easy to compile without WebP Version ( ) Support for reading from in-memory blobs Support for reading & writing TIFF metadata Add PHOTOMETRIC tag to TIFF (reported by Volker Hilsenstein) Support writing RGB TIFFs Version ( ) Fix hard crash when saving with non-existing file type Fix compilation on MacOS (patch by Alexander Bohn) Add verbose argument to tests.run() Better error when attempting to save floating point images Version ( ) Correctly accept uppercase extensions Python 3 support (patch by Christoph Gohlke [pull request 8 on github]) Read 1-Bit PNGs Read simple BMPs (compression and many bit types not supported) More complete debug mode (export DEBUG=2 when building), more checks Version ( ) Add lzw.cpp to source distribution Support saving 16-bit TIFF Better Mac OS support (patch from Alexander Bohn) 1.1. INSTALL 7

12 Version ( ) Fix imread_multi Version ( ) Add formatstr argument to imread Open files in binary mode on Windows (patch by Christoph Gohlke) Read-only support for LSM files Read-only support for XCF files (through xcf2png) Fix writing of non-contiguous images (at least PNG was affected) Version ( ) Add missing files to distribution Version 0.2 ( ) Compile on MSVC++ (Patches by Christoph Gohlke) Support for WebP Support for 1-bit TIFFs Better error message Support for multi-page TIFF reading Experimental read-only support for STK files Version 0.1 ( ) Support for PNG Support for TIFF Support for JPEG Bug Reports Please report any bugs either on github or by to If you have a test case where are not sure of whether imread is behaving correctly, you can discuss this on the pythonvision mailing list If at all possible, include a small image as a test case. 8 Chapter 1. Citation

13 CHAPTER 2 Indices and tables genindex modindex search 9