ImageMath Functions

Returns the reconstructed image at the specified pixel offset.

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Returns the reconstructed image at the pixel offsets represented by the interval.

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Computes the average of its arguments. If the arguments are images, the average is computed pixel-wise.

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Computes the average of its arguments with sigma clipping. If the arguments are images, the average is computed pixel-wise excluding outliers.

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Concatenates argument lists.

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Computes an exponential

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Computes the average of all pixels in each image. Unlike AVG which computes a pixel-by-pixel average across multiple images to produce a new image, IMG_AVG returns the average value of all pixels within an image. If multiple images are passed, returns a list of values. If a single image is passed, returns a number.

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Computes the sigma-clipped average of all pixels in each image. Unlike AVG2 which computes a pixel-by-pixel average across multiple images, IMG_AVG2 returns the sigma-clipped average value of all pixels within an image. If multiple images are passed, returns a list of values. If a single image is passed, returns a number.

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Returns the maximum value of all pixels in each image. Unlike MAX which computes a pixel-by-pixel maximum across multiple images to produce a new image, IMG_MAX returns the maximum value among all pixels within an image. If multiple images are passed, returns a list of values. If a single image is passed, returns a number.

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Computes the median of all pixels in each image. Unlike MEDIAN which computes a pixel-by-pixel median across multiple images to produce a new image, IMG_MEDIAN returns the median value of all pixels within an image. If multiple images are passed, returns a list of values. If a single image is passed, returns a number.

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Computes the sigma-clipped median of all pixels in each image. Unlike MEDIAN2 which computes a pixel-by-pixel median across multiple images, IMG_MEDIAN2 returns the sigma-clipped median value of all pixels within an image. If multiple images are passed, returns a list of values. If a single image is passed, returns a number.

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Returns the minimum value of all pixels in each image. Unlike MIN which computes a pixel-by-pixel minimum across multiple images to produce a new image, IMG_MIN returns the minimum value among all pixels within an image. If multiple images are passed, returns a list of values. If a single image is passed, returns a number.

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Returns the requested percentile of all pixels in each image. Generalizes IMG_MIN, IMG_MEDIAN and IMG_MAX, which correspond to percentiles 0, 50 and 100. When the percentile falls between two pixels, the value is linearly interpolated between them. Combined with a mask, this is the way to measure a reference level over a given region without a handful of aberrant pixels throwing it off. If multiple images are passed, returns a list of values. If a single image is passed, returns a number.

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Computes a logarithm

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Writes the statistics of an image to the log, then returns the image unchanged. Useful to understand how a value evolves from one image to the next in a batch, by wrapping an expression without changing its result.

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Computes the maximum of its arguments. If the arguments are images, the maximum is computed pixel-wise.

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Computes the median of its arguments. If the arguments are images, the median is computed pixel-wise.

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Computes the median of its arguments with sigma clipping. If the arguments are images, the median is computed pixel-wise excluding outliers.

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Computes the minimum of its arguments. If the arguments are images, the minimum is computed pixel-wise.

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Estimates the standard deviation of the noise of an image, by measuring the response of a Laplacian high pass filter. Smooth structures do not contribute to the measurement, unlike a percentile span, and the value remains reliable in the presence of a few aberrant pixels. Clipped or saturated areas, as well as defective pixels, are excluded from the measurement. Useful to assess the quality of each image of a batch, or to weight images before combining them. If multiple images are passed, returns a list of values.

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Fits a 2D polynomial surface to a mono image within the solar disk.

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Computes a power

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Rescales the pixel values of an image by multiplying each pixel by 65535, so that an image whose values are in the [0;1] range gets its values mapped to [0;65535]. Inverse of scale_to_unit.

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Rescales the pixel values of an image by dividing each pixel by 65535, so that an image whose values are in the [0;65535] range gets its values mapped to [0;1]. Useful for floating-point computations or interoperability with other tools.

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Deprecated: use the a - b subtraction, which now does exactly the same. Computes the signed difference between two images or scalars (a - b), without normalization.

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Computes a weighted average of images

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Computes a weighted average of images with sigma clipping. Combines the outlier rejection of AVG2 with the weighting of WEIGHTED_AVG: better images can be given a higher weight while aberrant pixels are still excluded. The result is not clamped, so that images normalized before stacking keep their full dynamic range.

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Generates an overlay of the detected active regions. This feature will only work if active region image generation has been selected.

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Returns the binning defined in the process parameters.

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Opens a dialog box to choose an image file.

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Opens a dialog box to choose multiple image files.

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Creates an image collage based on a text pattern. Use 'X' for images, '.' for empty cells, and '/' to separate rows. Spaces are ignored.

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Copies the metadata (observation date, observer, ray, process parameters, etc.) from from onto to and returns the resulting image. Useful when arithmetic operations merge metadata in an unwanted way, for example when subtracting a shared image overwrites each frame’s own observation date in a batch. Pixel values are not modified. If to and from are lists of the same length, the copy is done element-wise. If from is a single image and to is a list, every image in the list gets the same metadata.

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Triggers a new detection of the shape of the solar disk.

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The filter function can be used on a list of images to keep these which match a particular criteria. This can be particularly useful in batch mode. For example, you may want to perform a vertical and horizontal flip to images after a certain time, because of meridian flip.

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Returns the value of an element in a list at the specified position.

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Extracts the blue channel from an image.

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Extracts the green channel from an image.

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Extracts the red channel from an image.

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Creates a list from the parameters.

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Loads an image from a file.

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Loads many images from a directory.

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Downloads an image from the Solar Dynamics Observatory (SDO) taken as close as possible to a given date, in order to compare an observation with a space based image of the same moment. The image is cached on disk, so that it is only downloaded once. The solar disk is filled in automatically, so that the functions which rely on it can be used directly (autocrop2, disk_fill, annulus_mask, radius_rescale2, …​). SDO images are oriented with solar north up: remember to rotate your own image by the P angle (rotate_rad(img; angleP)) before comparing them.

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Converts a color image to grayscale.

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Executes inline Python code and returns the result. The script can use 'import jsolex' or 'from jsolex import …​' to access ImageMath functions.

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Executes a Python file (.py) and returns the result. The script can use 'import jsolex' or 'from jsolex import …​' to access ImageMath functions.

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Experimental, advanced function which is described specifically in this section.

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Creates an RGB image from three mono images.

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Saves an image and its metadata as raw (float) data, without any conversion to the displayable range. Unlike formats such as FITS or PNG, which requantize the pixels to 16 bits, the exact values are kept, so the image can be reloaded with load to debug a processing step in isolation. The image is returned unchanged, so the call can be inserted in a processing chain. If a list of images is given, each one is saved with its index appended to the file name.

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Combines two images side by side (left and right).

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Sorts a list of images

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Combines two images vertically (top and bottom).

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Returns the datetime when a video was recorded.

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Returns the wavelength of an image.

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Changes the working directory in which images are loaded by the LOAD and LOAD_MANY functions.

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Applies simple contrast adjustment by clipping values under the minimal value or above the maximal value.

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Applies a gamma correction to an image.

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Applies the inverse arcsin hyperbolic transformation to increase contrast.

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This function is a contrast enhancement function specifically designed for spectroheliograph images.

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Applies a Gaussian blur to an image.

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Applies CLAHE (Contrast Limited Adaptive Histogram Equalization) transformation to an image.

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Adaptive variant of CLAHE that averages several CLAHE passes at different tile sizes, derived automatically from the solar disk diameter. This multi-scale approach strongly reduces the bright limb ring that classic CLAHE produces.

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Limits the values of an image to a range. Values below the minimum are set to the minimum, values above the maximum are set to the maximum. Operations between images preserve out of range values, for example the negative values produced by a subtraction: this function brings them back into the displayable range when that is what you want.

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Applies a colorization to an image using a color profile related to the wavelength.

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Applies a colorization to an image using curve modeling. The curves are defined by 2 control points: the input value and the output value.

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Applies a curve transformation to an image. The transformation interpolates a polynomial of degree 2 passing through three points: the origin point (0,0), the curve point (in, out), and the extreme point (255,255).

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Attenuates reflections (ghosts) of the solar disk, including several at once, by subtracting a smooth estimate of their excess brightness, without removing the underlying detail. Everything is derived from the image, with no position parameter.

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Removes horizontal banding (stripes) from an image. With ellipseMode 2, an additional fine stage also removes localized streaks from the sky, such as the short trails drawn next to the limb by the halo of a bright region, while preserving prominences and coronal structures, which are taller.

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Fills the detected solar disk with a given value (default is the value of the detected black point).

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Equalizes the histogram of the images in parameter so that they all have about the same brightness.

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Applies a banding correction to the image

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Applies geometric correction to the image based on the calculated ellipse

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Computes an artificial flat field image to correct the image then applies the correction.

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Inverts the colors of an image.

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Shifts the image up so that it no longer contains negative values, by adding the same amount to every pixel. An image which contains no negative value is left unchanged. Useful after a subtraction, which preserves negative values, when you want to keep them rather than discard them with CLAMP.

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Stretches the histogram of an image to occupy the entire range of possible values. This function can also be used to compress the values of an image into the range of possible values (for example after an exponential calculation).

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Applies a Midtone Transfer Function (MTF) with configurable parameters for shadows, midtones and highlights. Allows precise control over tonal transformation.

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Applies an autostretch algorithm using Midtone Transfer Function (MTF) that automatically adjusts contrast based on histogram analysis. Uses sigma-based shadow clipping and target background level.

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Stretches histogram by mapping specified percentiles to black and white points.

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Applies the Richardson-Lucy deconvolution algorithm to the image.

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Saturates the colors of an image.

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Applies a sharpening filter to an image.

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Applies a sigmoid (S-curve) transformation for smooth contrast enhancement.

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Applies an unsharp mask to an image.

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Automatically crops an image around the solar disk. The dimensions of the cropping area are determined by the ellipse but also by the dimensions of the image. It is better to use the autocrop2 function which guarantees a centered and square crop.

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Crops an image to a centered and square area around the solar disk.

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Crops an image to the specified coordinates and dimensions.

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Generates a list of images corresponding to the detected sunspots. Each image is named after the NOAA active region it shows, when it can be identified, and the separate parts of a single region are grouped into a single image.

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Reduces the image to the specified dimensions, ensuring that the center of the solar disk will be at the center of the image. There is no scaling: if the solar disk does not fit within the target dimensions, it will be cropped.

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Creates a BACKGROUND model from an image, which can be used to subtract the BACKGROUND from the original image.

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Creates the column illumination model of an image: a background level which changes from one column to the next but stays constant along a column. In spectroheliography one column of the image comes from one frame of the video, so the light scattered inside the instrument while the slit crosses the solar disk raises the background of all those columns, which produces a dome of excess background peaking at the middle of the disk and falling steeply just past its edges. No line by line correction, such as destripe, can see it. The level of each column is the median of its sky pixels, lightly smoothed along the image: no shape is imposed, so the steep fall at the edges of the disk is followed faithfully instead of being rounded off. The model can then be subtracted from the image, or used as a divisor after normalization.

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Removes the background veil around the solar disk, caused by light scattered inside the instrument. It shows up as a bright band extending above and below the disk, and stopping to its left and right. The disk itself is not modified, and prominences and corona are preserved. Also works on images which have already been stretched.

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This is a function similar to remove_bg that uses a polynomial modeling of the background to remove gradients. This function can be used on images without ellipse information (solar disk).

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Performs background removal on an image. This can be used when the contrast is very low (e.g in helium processing) and that stretching the image also stretches the background. This process computes the average value of pixels outside the disk, then uses that to perform an adaptative suppression depending on the distance from the limb, in order to preserve light structures around the limb.

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Adjusts the canvas size of images so they all have the same dimensions, without rescaling the solar disk. Unlike radius_rescale, this function does not modify the disk size, which avoids adding distortion. It uses the detected ellipses to center each solar disk in a common canvas. The final canvas size is computed automatically to contain all disks.

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Flips an image horizontally.

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Relative scaling method which can facilitate mosaic composition. It will therefore most likely be used in batch mode. It allows rescaling a set of images so that they all have the same solar disk radius (in pixels). In order to do so, it will perform an ellipse regression against each image to compute their solar disk, then will rescale all images to match the radius of the largest one.

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Rescales an image to have a specific solar radius (in pixels) while maintaining the specified final dimensions. The solar disk is centered in the resulting image. Instead of giving these values, you can supply a reference image with ref: the image will then be rescaled to have the same solar radius and the same dimensions as it, leaving the reference image untouched.

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Rescales an image to the specified absolute dimensions.

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Rescales an image by applying a rescaling factor.

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Applies a rotation to an image, in degrees.

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Applies a left rotation to an image

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Applies a rotation to an image, in radians.

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Applies a right rotation to an image

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Flips an image vertically.

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Computes the number of pixels corresponding to a distance in Angstroms. The distance is determined by calculating the dispersion, which will only be correct if you have correctly specified the pixel size of the camera, as well as your spectroheliograph.

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Returns the average image computed from the SER file frames. If the corrected parameter is set to 1, the image is corrected for distortion (polynomial curve straightened).

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Generates a continuum image around the studied line. This function differs from the classic continuum image in that it is not a single image calculated by the difference of fixed pixels of 15 pixels, but an image calculated from the median of a set of images.

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Computes a pixel offset relative to the detected line. The distance is determined by calculating the dispersion, which will only be correct if you have correctly specified the pixel size of the camera, as well as your spectroheliograph.

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Computes the number of angstroms corresponding to a distance in pixels. The distance is determined by calculating the dispersion, which will only be correct if you have correctly specified the pixel size of the camera, as well as your spectroheliograph.

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Draws an arrow on the image.

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Draws a circle on the image.

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Draws the Earth on the image, to the scale of the solar disk

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Draws a globe whose orientation and diameter correspond to the detected solar parameters.

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Displays observation details on the image

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Draws a rectangle on the image.

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Displays solar parameters on the image

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Draws text on the image. The text can include the following variables:

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Creates an animation from a series of images.

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Interpolates images between them. By default, the interpolation is linear and it will create exactly the specified number of images. However, if a unit is specified, then the behavior will be different: the number of steps corresponds to the number of images to create, for a given time unit, for the time elapsed between the two images. For example, if one image was taken at 10:00 and the other at 10:02, and the unit is ipm, that the number of steps is 10, then 20 images will be created. This allows creating smoother transitions when SER files were not recorded at regular intervals.

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Allows to correct the distortion of an image. It has 2 distinct modes of use. In the first mode, it takes a reference image and an image to correct, as well as 3 optional parameters: the tile size, the sampling, and the sky background value. The returned image will be corrected as closely as possible to the reference image, making it usable for stacking, for example. In the second mode, it takes a list of images to correct and a list of already corrected images, in which case the correction parameters for each image are taken using the same index image in the list of already corrected images. This can be useful, for example, when calculating the distortion at the center of the line (shift 0) and wanting to apply the same corrections to images with different shifts. For best results, use consensus reference mode (stack_ref with select='consensus') combined with sparse=1.

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Creates a mosaic of images.

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Stacks multiple images.

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Stacks de-distorted images by applying a weight to each image. The weight is calculated based on the de-distortion error: images requiring strong distortion correction will have a lower weight.

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Selects a reference image for stacking. For best results, use consensus mode combined with sparse=1 in the dedistort function.

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Creates an annulus-shaped mask around the solar disk, with radii expressed in solar radii. The mask can be passed to the functions which accept a mask parameter (percentile_stretch, mtf_autostretch, …​) to restrict the pixels taken into account when computing their statistics, while still transforming the entire image. Use rmin=0 for a disk mask. Requires a detected solar disk.