Resample Nifti Image Python

An image can be loaded from a file in a variety of formats, and is extensible to new formats via image format handlers. When we are scaling by a non-integer value, we need to interpolate values appropriately, so that the quality of the image is maintained. Image Module — Pillow (PIL Fork) 4. Ideally this transformation would be paired with appropriate updating of the header (SFORM and QFORM shou…. Datacamp provides online interactive courses that combine interactive coding challenges with videos from top instructors in the field. modules; NiLearn Home | nilearn. Image Class. Python sentiment analysis using NLTK text classification with naive bayes classifiers and maximum entropy classififiers. The principle here is a Python principle, which is that everything is a pointer. #!/usr/bin/python # The contents of this file are in the public domain. x if required. resize_cover(image, size, validate=True, resample=Image. convert_dicom dicom2nifti. The Output Cell Size parameter can resample the output to the same cell size as an existing raster layer, or it can output a specific X and Y cell size. 0 mm resolution and keep the images aligned. MAJORITY — Determines the value of each pixel based on the most popular value within a 3 by 3 window. NET virtual machines. nifti_masker. NIfTI-1 is a binary file format for storing medical image data, e. One thing that might be nice though is to create something like a python version of fslreorient2std, which would allow a user to specify, in a simple way, that they would like an image (or all of their images) to be reoriented into a standard convention (e. Recently some users reported that a handful of datasets hosted on OpenfMRI contained NIfTI files with ambiguous orientation information. FSLUTILS is a set of useful command-line utilities which allow the conversion, processing etc. Thanks to Pedro’s post, I was finally able to create a zoomable image viewer using GDAL and Leaflet. Most of you are familiar with image data, taken with ordinary cameras (these are often called “natural images” in the scientific literature), but also with specialized instruments. , of the Penn Image Computing and Science Laboratory (PICSL) at the University of Pennsylvania, and Guido Gerig, Ph. As someone who works with time series data on almost a daily basis, I have found the pandas Python package to be extremely useful for time series manipulation and analysis. This is particularly sad, because there is a large number of easy-to-use, high-quality libraries for signal processing available for Python (e. Python Pandas - DataFrame - A Data frame is a two-dimensional data structure, i. signal; masking; version; __init__; input_data. Niftilib is a set of i/o libraries for reading and writing files in the nifti-1 data format. The function is supposed to use the aspect ratio of the source image to calculate the V output dimension. Convert DICOM images to JPEG, PNG, TIFF, or BMP format. We use cookies for various purposes including analytics. How do I do that ? If you know any other Python library that can do it, it would also work. These assume that the WCS information contained in the data are correct. Using the Python Image Library (PIL) you can resize an image. Resampling involves changing the frequency of your time series observations. The principle here is a Python principle, which is that everything is a pointer. Image data is made available via NumPy arrays. In an attempt to identify the best tools available, this review compares images enlarged using several digital image interpolation (resizing / resampling) methods including S-Spline, Genuine Fractals, Lanczos, Bicubic, Stair Interpolation, Kneson (standard), QImage (Vector, Pyramidal), pxl SmartScale, PhotoZoom Pro 2, Pictura, Resize IT, Blow Up. Documentation and code by the Insight Software Consortium is licensed under a Creative Commons Attribution 3. Named after Monty Python's Eric Idle, Eric is actually written in Python using the Qt framework. We also provide the option to resample the data to an orthogonal nifti. 7 mm), greatly increases the data size and slows down everything. NumPy is the library that gives Python its ability to work with data at speed. The module also provides a number of factory functions, including functions to load images from files, and to create new images. If the header information conforms to the nifti-1 standard, the information is stored in property "nifti" as an object of class NiftiHeader. Explore connectivity data and learn the application with our tutorial and sample HCP data set. You can change this behavior with the resample() or reduceResolution() methods. I'm trying to resample a GeoTIFF file to match another raster layer using python GDAL package. By default support for gantry tilted ct is disabled as we validate image orthogonality. This class encapsulates a platform-independent image. interpolation. Datacamp has beginner to advanced Python training that programmers of all levels benefit from. We recommend representing the anatomy and class files at 1 mm (isovoxel). It provides specialty ops and functions, implementations of models, tutorials. In this paper, we presented a very flexible tool that can be used as an effective alternative to classical polynomial interpolation. For the z direction, you will need to interpolate (reslice) the z direction from 2. I try your 'DICOM Processing and Segmentation in Python'. It is oriented toward extracting physical information from images, and has routines for reading, writing, and modifying images that are powerful, and fast. The only problem is that since it uses PIL, the numpy array has to conform to image formats, giving me a maximum of 4 "color" channels. In our previous Python Library tutorial, we saw Python Matplotlib. 1,语言python2. This can be easily achieved using nibabel package with only few lines of code. Solved it, it seems that the conversion from ECW to TiFF either when resampling or mosaicing the tiles to a new raster only works with Python 32 bit and not Python 64 bit. You can pass parameters like resulting image size, pixel resampling filter and the box region of source to be considered. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy. Nifti1Image () Examples. INTER_AREA for shrinking and cv. im1 (2D numpy array) – The second (subject) image numiter ( int ) – How many times to iterate when determining scale and rotation order ( int ) – Order of approximation (when doing transformations). Find Software Select Programs from the menu above to search for software, or click this button. I try your 'DICOM Processing and Segmentation in Python'. I couldn't find a clear tutorial. Example Image Analysis with Keras In order to explain image processing with keras, we will use data from Kaggle competition — dogs and cats. This package does not do image registration, which is the process of aligning images where one or more images may have incorrect or. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy. Using PyNIfTI one can easily read and write NIfTI and ANALYZE images from within Python. img file pair for each 3D/4D image ; NIFTI - the NIFTI-1 format but in a single. Mathematical. We only review how to compute pixel values here. # Resample # resamples 20x20 mm of originalImage - the origin is defined by the reference identified by referenceName # the resulting image is of size 60 x 60 pixels and set to image imageName #-----def Resample(originalImage,referenceName,imageName): sub_x = 20. 我们使用python处理该类型的数据. Numpy has two different ways of indexing arrays in memory, C and fortran. Your code should be general enough to take in images or kernels of different sizes. To find the transformation matrix, we need three points from input image and their corresponding locations in output image. If the header information conforms to the nifti-1 standard, the information is stored in property "nifti" as an object of class NiftiHeader. Trackvis or NIfTI YOH (Dartmouth) NeuroDebian Munich, Germany 2012 8 / 20. Scikit-image is often compared to OpenCV, a collection of programs for computer vision that include live video. Most often, these data. Their syntax is generally the same as MATLAB's plotting syntax. We also provide the option to resample the data to an orthogonal nifti. geotiff, then resample or mosaic the images). This library supports many file formats, and provides powerful image processing and graphics capabilities. This will incur interpolation blurring but is guaranteed to. You can explicitly allow gantry tilted data by disabling this validation. There are Linux, Macintosh, and Windows versions of the. Numpy also has a great Numpy for Matlab users section which compares common MATLAB commands to their equivalent expressions in Numpy. This file is used to construct the heuristic. You should configure the padding value and spline interpolation order. It is oriented toward extracting physical information from images, and has routines for reading, writing, and modifying images that are powerful, and fast. Join Julieanne Kost for an in-depth discussion in this video Using Image Size to resize or resample an image, part of Photoshop CC 2015 Essential Training Lynda. I want to down-sample it to an image with 2. For computers, this task is somewhat more difficult: they need to understand the basic structure of the image, locate edges which might indicate a horizon, and pare out the edges which do not matter. Indeed, it can be used to provide additional structure or insight into the learning problem for supervised learning models. This issue can make distinguishing between the left and right brain hemispheres virtually impossible without some external reference (like a fiducial marker). Resampling datasets with anisotropic voxels to isotropic Visualizing multiple brains simultaneously Finding track correspondence between different brains Warping tractographies into another (e. Layout is unimportant, I don’t care were the source image is located on the page. Python Pillow – Rotate Image 45, 90, 180, 270 degrees. The image is loaded by nibabel. See the Package overview for more detail about what's in the library. The Pandas library in Python provides the capability to change the frequency of your time series data. We use cookies for various purposes including analytics. You can save your output to BIL, BIP, BMP, BSQ, DAT, GIF, GRID, IMG, JPEG, JPEG 2000, PNG, TIFF, or any geodatabase raster dataset. Spectral Python (SPy) is a pure Python module for processing hyperspectral image data. To resize an image, OpenCV provides cv2. registration. The different FSLUTILS programs are: fslascii2img - convert ASCII text file to image file. Specific objectives are. 3Albers Equal-Area TheAlbers equal-area conic projectionis a projection that is useful where area needs to be pre-served for large geographical areas. header (nibabel header): the nibabel header to use as header for the nifti file. I have little knowledge in MRI image manipulation. Output Histograms:Determines whether to output. MedPy is a library and script collection for medical image processing in Python, providing basic functionalities for reading, writing and manipulating large images of arbitrary dimensionality. We also provide the option to resample the data to an orthogonal nifti. Documentation and code by the Insight Software Consortium is licensed under a Creative Commons Attribution 3. You will need a volume viewer to view the resulting defaced file. Using gdal I want to resample (in this case, oversample) a DEM. In python, we will apply 2-D convolution to two images, 'kitten. It is the product of a decade-long collaboration between Paul Yushkevich, Ph. If the header information conforms to the nifti-1 standard, the information is stored in property "nifti" as an object of class NiftiHeader. The voxel size is 1. d: dicom2nifti dicom2nifti. The only problem is that since it uses PIL, the numpy array has to conform to image formats, giving me a maximum of 4 "color" channels. #!/usr/bin/python # The contents of this file are in the public domain. It doesn’t gzip the output image, like the fslmerge script, but, it’s scriptable using the ‘View>Show. 2-3ubuntu1) lightweight database migration tool for SQLAlchemy. Functions help break our program into smaller and modular chunks. [Freesurfer] FW: convert (resample) fsaverage/mri/aseg. scikit-image is a collection of algorithms for image processing. from astropy. Using PyNIfTI one can easily read and write NIfTI and ANALYZE images from within Python. Layout is unimportant, I don't care were the source image is located on the page. I have used fsl prelude to unwrap my mri images, and they are now in the nifti format. Extra information can be included in the nifti format in a number of ways as allowed by the standard. com courses again, please join LinkedIn Learning. On the one hand, this is convenient, but sometimes, you need to perform this task as a intermediate step, and creating and deleting files is tedious and error-prone. The Python Imaging Library allows you to store several bands in a single image, provided they all have the same dimensions and depth. We have collected a list of Python libraries which can help you in image processing. By voting up you can indicate which examples are most useful and appropriate. Another important feature is that, even if the image was a darker image (instead of a brighter one we used), after equalization we will get almost the same image as we got. Answers: Often. magnetic resonance image (MRI) and functional MRI (fMRI) brain images. It can be used interactively from the Python command prompt or via Python scripts. masker_validation; input_data. Sample Python code to use PDFTron SDK's built-in rasterizer to render PDF images on the fly and save the resulting images in various raster image formats (such as PNG, JPEG, BMP, TIFF). Resample a signal with scipy. It doesn’t gzip the output image, like the fslmerge script, but, it’s scriptable using the ‘View>Show. scikit-image is a collection of algorithms for image processing. Kernel density estimation using Python, matplotlib. There are several conceivable ways to concatenate images of different sizes. To view NiFTI files, use the following programs: ImageJ, a java-based program that runs on most operating systems, including MAC OSX; MBAT, from the Laboratory of Neural Imaging at USC. Updated Orientation Information in NIfTI Headers. Standard this will result in a nifti file where the gantry tilt is captured by the affine matrix. Downsizing the Data Set – Resampling and Binning of Time Series and other Data Sets Using Elastic Stack, Filebeat (for log aggregation) Prepare Jupyter Notebook Workshop Environment through Docker container image and Bootstrap Notebook. resample_img specifies the resampling in terms of the target_affine to match the spatial configuration defined by the new affine. It returns a tuple of height,width and channel(if image RGB color) ex:(height,width,channel) as (360,480,3) Different interpolation methods are used to resize the image. compressed_dicom dicom2nifti. I usually want to do this for photos that I want to email or post on a website since some of my images can be quite large. Two common applications are: Downsampling: combining pixel data to decrease size; Upsampling: distributing pixel data to increase size ; For this exercise, transform and then resample the brain image (im) to see how it affects image shape. For computers, this task is somewhat more difficult: they need to understand the basic structure of the image, locate edges which might indicate a horizon, and pare out the edges which do not matter. Now copy the dicominfo. magnetic resonance image (MRI) and functional MRI (fMRI) brain images. nifti-1 is a binary file format for storing medical image data, e. Unless image resizing or datatype conversion must be performed the image data can be shared by the NIfTI image and accessing NumPy arrays, and. Python SciPy Tutorial – Objective. affine_transform. resample() function is primarily used for time series data. Resample Image to Size in Pixels With ImageMagick. gaussian_kde. Pandas dataframe. Updated Orientation Information in NIfTI Headers. , data is aligned in a tabular fashion in rows and columns. What is Resampling? When resampling data to a new grid (e. MedPy is a library and script collection for medical image processing in Python, providing basic functionalities for reading, writing and manipulating large images of arbitrary dimensionality. There are several conceivable ways to concatenate images of different sizes. To resize an image, OpenCV provides cv2. The random. A common issue with resampling resulting in an all black image is due to (a) incorrect specification of the desired output image's spatial domain (its meta-data); or (b) the use of the inverse of the transformation mapping from the. We pride ourselves on high-quality, peer-reviewed code, written by an active community of volunteers. com courses again, please join LinkedIn Learning. The resampled vtkImageData object is stored under imageResampled. The ANALYZE format was originally developed in conjunction with an image processing system (of the same name) at the Mayo Foundation. Resize and crop (from center) the image so that it covers a 200x100 rectangle. I have little knowledge in MRI image manipulation. ResampleImageFilter resamples an existing image through some coordinate transform, interpolating via some image function. png', both are RGB pictures, so you will have to apply 2-D convolution to all three channels. The getImageData() method returns an ImageData object that copies the pixel data for the specified rectangle on a canvas. Visualizing brain images¶ Once that NIfTI data are loaded, visualization is simply the display of the desired slice (the first three dimensions) at a desired time point (fourth dimension). Your question would be easier to answer if you describe what you mean by ". resample_poly¶ scipy. LANCZOS, bg_color=(255, 255, 255, 0)) Resize the image so that it can fit in the specified area, keeping the ratio and without crop. Cygrid can be used to resample data to any collection of target coordinates, although its typical application involves FITS maps or data cubes. The NiftiImage class provides Python-style access to the full header information. Standard this will result in a nifti file where the gantry tilt is captured by the affine matrix. Analyze format and Nifti format are the data formats that supported by DiffusionKit. tsv file out of the hidden. Python Programming tutorials from beginner to advanced on a massive variety of topics. Its main contributions are n-dimensional versions of popular image filters, a collection of image feature extractors,. For computers, this task is somewhat more difficult: they need to understand the basic structure of the image, locate edges which might indicate a horizon, and pare out the edges which do not matter. Python is a great language for doing data analysis, primarily because of the fantastic ecosystem of data-centric python packages. niftyreg_image_resampling package » niftynet. Matlab, Pyzo can be considered a free alternative. Originally, launched in 1995 as ‘Numeric,’ NumPy is the foundation on which many important Python data science libraries are built, including Pandas, SciPy and scikit-learn. I now need to compare these to images with images that I have unwrapped with a matlab algoritm that i made myself. Moreover, it is not. To resize an image, OpenCV provides cv2. A small library (written in C) allowing 2D or 3D image resampling using a 4x4 matrix. We use cookies for various purposes including analytics. Produces the smoothest image but can create values outside of the range found in the source data. Up-sampling (increasing resolution) raster image using GDAL? using python gdal. This will incur interpolation blurring but is guaranteed to. Named after Monty Python's Eric Idle, Eric is actually written in Python using the Qt framework. Resample an image via a coordinate transform. In simple words, the filter() method filters the given iterable with the help of a function that tests each element in the iterable to be true or not. To rotate an image by an angle with Python Pillow, you can use rotate() method on the Image object. Working with four-dimensional data []. Imbalanced classes put "accuracy" out of business. I usually want to do this for photos that I want to email or post on a website since some of my images can be quite large. A Map object consists of a data array endowed with a coordinate system and combined with meta data. DLTK, the Deep Learning Toolkit for Medical Imaging extends TensorFlow to enable deep learning on biomedical images. LANCZOS) Resize the image to fill the specified area, crop as needed. datetime64 data type. Viewing 3D Volumetric Data With Matplotlib In this Python tutorial, you'll make use of Matplotlib's event handler API to display the slices of an MRI data set. How do I do that ? If you know any other Python library that can do it, it would also work. The Image module provides a class with the same name which is used to represent a PIL image. 2 freeware GUI for ImageMagick (by Francesco Mondello) today:. > I and a colleague are working on an image segmentation problem, where we use > marching cubes to generate the surface of a segmentation, apply a custom > smoothing operation to the surface mesh with numpy in python, then re-render > as a vtk image at an arbitrary higher resolution before writing out for the > rest of our workflow. The goal of this competition is to develop an algorithm to classify whether images contain either a dog or a cat. Extra information can be included in the nifti format in a number of ways as allowed by the standard. Image Resampling Pipeline • In practice: Resampling with low-pass filter in order to reduce aliasing artifacts. ResampleImageFilter resamples an existing image through some coordinate transform, interpolating via some image function. Class Resample: Def Resize(self, Image, Fx=None, Fy=None, Interpolation=None): """calls The Appropriate Funciton To Resample An Image Based On The Interpolation Method Svn. Most of the ways I found online is to use gdalwarp resample data from the command line. destroyAllWindows() 4. You will need a volume viewer to view the resulting defaced file. There are four options for the Resampling Technique parameter: Nearest —Performs a nearest neighbor assignment and is the fastest of the interpolation methods. Normal people use an image editor. Baby Names, 1880-2010 Hello Readers, Here in the third part of the Python and Pandas series , we analyze over 1. I have 500 x 500 arrays of floats, representing 2D "grayscale" images, that I need to resample at a lower spatial resolution, say, 120 x 120 (details to follow, if you feel they are relevant). Resampling Data¶. Pyresample is designed for resampling of remote sensing data and supports resampling from both fixed grids and geolocated swath data. Gantry tilted CT. This is the third post showing how to resample an image: I first covered SPM, then wb_command. By default support for gantry tilted ct is disabled as we validate image orthogonality. Recommended Python Training - DataCamp. Any object in python can be pickled so that it can be saved on disk. Command line:. You can pass parameters like resulting image size, pixel resampling filter and the box region of source to be considered. I have 500 x 500 arrays of floats, representing 2D "grayscale" images, that I need to resample at a lower spatial resolution, say, 120 x 120 (details to follow, if you feel they are relevant). Produces the smoothest image but can create values outside of the range found in the source data. 43 KB import math from PIL import Image. Read/Write both NIfTI-1 and NIfTI-2 image files. Interpolation of an image Given a random-sampled selection of pixels from an image, scipy. resize bash You can resample an entire directory of images in. Unlike R, a -k index to an array does not delete the kth entry, but returns the kth entry from the end, so we need another way to efficiently drop one scalar or vector. Thermal images were collected at the end of winter and at night to maximize temperatures between warmer discharging groundwater and colder surface waters. The Python Imaging Library allows you to store several bands in a single image, provided they all have the same dimensions and depth. It’s common when first learning NumPy to. def _resample_gantry_tilted (original_image): """ In this function we will create an orthogonal image and resample the original data to this space In this calculation we work in 3 spaces / coordinate systems - original image coordinates - world coordinates - "projected" coordinates This last one is a new rotated "orthogonal" coordinates system. The current free version is PIL 1. Among them, scikit-image is for image processing in Python. 2 and newer, including 2. The GUI is located within the Batch Editor’s SPM>Util menu, and be default saves the specified 3D NIFTI images to a single 4D NIFTI image within the same directory. NIfTI, CIFTI, GIFTI in the HCP and Workbench: a primer The HCP is releasing preprocessed data in both volumetric NIfTI and surface/volumetric CIFTI formats. # Resample # resamples 20x20 mm of originalImage - the origin is defined by the reference identified by referenceName # the resulting image is of size 60 x 60 pixels and set to image imageName #-----def Resample(originalImage,referenceName,imageName): sub_x = 20. Today, we bring you a tutorial on Python SciPy. (2006), First we mathematically model and generalize our approach. Magnetic Resonance Imaging dataset acquisition, usually entails the conversion of image data from the native scanner format to a format suitable for the intended analysis. Imbalanced classes put "accuracy" out of business. I've even tried running -density 72x72 to specify the new density, but that doesn't seem to work either. The freesurfer package includes the 'freeview' viewer, but there are many others capable of reading dicom and nifti volumes. In this tutorial, you will discover how to use Pandas in Python to both increase and decrease. This package does not do image registration, which is the process of aligning images where one or more images may have incorrect or. jpg) using PIL to a width of 300 pixels, which is set in the variable basewidth and a height proportional to the new width. DCM2NII is a stand-alone program that is distributed with MRIcron. To create complete models, glossy surfaces as well as occlusions in the data must be accounted for. linspace(0, 5, 100) x = np. com/en/entry/1130. Niftilib is a set of i/o libraries for reading and writing files in the NIfTI-1 data format. Utilities to process your images before performing an inference. When working with data, as is needed when interpolating data over such an area. Your question would be easier to answer if you describe what you mean by ". resample¶ scipy. GDAL allows this by defining in-memory raster files. The API for compressing PDF files. This produces the smoothest image but can create values outside of the range found in the source data. I want to down-sample it to an image with 2. Resampling T1 anatomicals (nifti class files) To resample the T1 & class files use the command mrGrayResampleNiftiClass(t1File, classFile, outMm) N. How to Rotate Images in Python Using a Horizon Detection Algorithm When we look at an image, it’s fairly easy to detect the horizon line. 1 = linear, 3 = cubic etc. Trackvis or NIfTI YOH (Dartmouth) NeuroDebian Munich, Germany 2012 8 / 20. The new resampled images will be written back out to a specified directory. ResampleImageFilter resamples an existing image through some coordinate transform, interpolating via some image function. The class is templated over the types of the input and output images. Works for CT and MR and image_defl. Unlike R, a -k index to an array does not delete the kth entry, but returns the kth entry from the end, so we need another way to efficiently drop one scalar or vector. Additionally some image manipulation scripts are installed under the medpy_-prefix which offer various functionalities. Pyresample is a python package for resampling geospatial image data. On my last project I hacked a bit with HTML and CSS to develop responsive styles - which can be a pain. The class is templated over the types of the input and output images. Thankfully, frameworks such. An image can be created from data, or using wx. Montage is available as a g-zipped tar file. Flexible Data Ingestion. Now copy the dicominfo. In the QGIS Processing Toolbox, the gdalogr:warpproject algorithm is used, which is the same as the algorithm used for reprojection. If you find missing recipes or mistakes in existing recipes please add an issue to the issue tracker. 0 is also supported. An image can consist of one or more bands of data. Pixelate image in python Raw. Image processing analytics has applications from processing a X-Ray to identifying stationary objects in a self driving car. The size of an image can be changed using the resize() method of the Image class of Pillow - the Python Image Processing Library. I've even tried running -density 72x72 to specify the new density, but that doesn't seem to work either. In this tutorial, you will discover how to use Pandas in Python to both increase and decrease. Resampling involves changing the frequency of your time series observations. resize_cover(image, size, validate=True, resample=Image. ITK-Snap correctly reads image header but it does not support editing in oblique planes, so you need to resample the input images manually. m function is the most flexible of the main BRAVO functions. This package provides the tools that are shipped with the library (nifti_tool, nifti_stats and nifti1_test). By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy. resize_cover(image, size, validate=True, resample=Image. In simple words, the filter() method filters the given iterable with the help of a function that tests each element in the iterable to be true or not. techniques for image transformation and resampling. #!/usr/bin/python # The contents of this file are in the public domain. Also, the aspect ratio of the original image could be preserved in the resized image. def Sinc. Technically, image resizing is a simplified form of Image Distortion, both of which are techniques of image resampling. This class encapsulates a platform-independent image. They include python code, PNG images, and descriptions of what the example is doing. Image data is made available via NumPy arrays. Downsizing the Data Set – Resampling and Binning of Time Series and other Data Sets Using Elastic Stack, Filebeat (for log aggregation) Prepare Jupyter Notebook Workshop Environment through Docker container image and Bootstrap Notebook. I want to down-sample it to an image with 2. If your image data is in DICOM format, you need to convert the data into Nifti format. Unfortunately, it is not that trivial to read NIfTI images with Python. It also makes it easy to apply the same set of operations to a number of images.
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