coronalyze.core.image_transforms

coronalyze.core.image_transforms#

Image transformation utilities using high-precision cubic splines.

Provides sub-pixel image shifts and flux-conserving resampling for coronagraphic image analysis. All functions are JIT-compilable and differentiable.

Functions#

ccw_rotation_matrix(rotation_deg)

Return the counter-clockwise rotation matrix for a given angle.

shift_image(image, shift_y, shift_x[, order, mode, cval])

Shift an image with sub-pixel precision using cubic splines.

resample_flux(f_src, pixscale_src, pixscale_tgt, shape_tgt)

Resample an image onto a new grid while conserving total flux.

Module Contents#

coronalyze.core.image_transforms.ccw_rotation_matrix(rotation_deg)[source]#

Return the counter-clockwise rotation matrix for a given angle.

Args:

rotation_deg: Rotation angle in degrees. Positive = counter-clockwise.

Returns:

2x2 rotation matrix as a JAX array.

Parameters:

rotation_deg (float)

Return type:

jax.Array

coronalyze.core.image_transforms.shift_image(image, shift_y, shift_x, order=3, mode='constant', cval=0.0)[source]#

Shift an image with sub-pixel precision using cubic splines.

Essential for planet injection where source positions are sub-pixel aligned. Uses inverse mapping: to shift content by (+dy, +dx), sample from (y-dy, x-dx).

Args:

image: 2D input image. shift_y: Shift in Y direction (pixels). Positive = Down. shift_x: Shift in X direction (pixels). Positive = Right. order: Interpolation order (3 = cubic splines, recommended for HCI). mode: Boundary handling mode (‘constant’, ‘nearest’, ‘wrap’, ‘mirror’, ‘reflect’). cval: Value to use for ‘constant’ mode outside boundaries.

Returns:

Shifted image with same shape as input.

Parameters:

  • image (jax.Array)

  • shift_y (float)

  • shift_x (float)

  • order (int)

  • mode (str)

  • cval (float)

Return type:

jax.Array

coronalyze.core.image_transforms.resample_flux(f_src, pixscale_src, pixscale_tgt, shape_tgt, rotation_deg=0.0)[source]#

Resample an image onto a new grid while conserving total flux.

Performs an affine transformation (rotation and scaling) to map the source image onto a target grid. Converts to surface brightness, interpolates, then converts back to integrated flux per pixel.

Args:
f_src:

The source image (2D array) containing integrated flux values per pixel. Shape: (ny_src, nx_src).

pixscale_src:

The pixel scale of the source image (e.g., arcsec/pixel or lambda/D). Must be in the same units as pixscale_tgt.

pixscale_tgt:

The pixel scale of the target image. Must be in the same units as pixscale_src.

shape_tgt:

The shape of the target image (ny_tgt, nx_tgt).

rotation_deg:

Rotation angle in degrees. Due to inverse mapping, this rotates the image content clockwise in the output. This matches coronagraphoto’s convention exactly.

Note: Rolling a telescope CCW produces a CW rotation in the image, so this convention aligns with physical telescope roll angles.

Returns:

The resampled image on the target grid with total flux conserved. Shape: (ny_tgt, nx_tgt).

Parameters:

  • f_src (jax.Array)

  • pixscale_src (float)

  • pixscale_tgt (float)

  • shape_tgt (tuple[int, int])

  • rotation_deg (float)

Return type:

jax.Array

Contents