blot_image

drizzle.resample.blot_image(data, pixmap, pix_ratio, exptime, output_pixel_shape, interp='poly5', sinscl=1.0)[source]

Resample the data input image onto an output grid defined by the pixmap array. blot_image performs resampling using one of the several interpolation algorithms and, unlike the “drizzle” algorithm with ‘square’, ‘turbo’, and ‘point’ kernels, this resampling is not flux-conserving.

This method works best for with well sampled images and thus it is typically used to resample the output of Drizzle back to the coordinate grids of input images of Drizzle.add_image(). The output of Drizzle are usually well sampled images especially if it was created from a set of dithered images.

Parameters:

  • data (2D array) – Input numpy array of the source image in units of ‘cps’.

  • pixmap (3D array) – A mapping from input image (data) coordinates to resampled (out_img) coordinates. pixmap must be an array of shape (Ny, Nx, 2) where (Ny, Nx) is the shape of the input image. pixmap[..., 0] forms a 2D array of X-coordinates of input pixels in the ouput frame and pixmap[..., 1] forms a 2D array of Y-coordinates of input pixels in the ouput coordinate frame.

  • output_pixel_shape (tuple of int) – A tuple of two integer numbers indicating the dimensions of the output image (Nx, Ny).

  • pix_ratio (float) – Ratio of the input image pixel scale to the ouput image pixel scale.

  • exptime (float) – The exposure time of the input image.

  • interp (str, optional) –

    The type of interpolation used in the resampling. The possible values are:

    • ”nearest” (nearest neighbor interpolation);

    • ”linear” (bilinear interpolation);

    • ”poly3” (cubic polynomial interpolation);

    • ”poly5” (quintic polynomial interpolation);

    • ”sinc” (sinc interpolation);

    • ”lan3” (3rd order Lanczos interpolation); and

    • ”lan5” (5th order Lanczos interpolation).

  • sincscl (float, optional) – The scaling factor for “sinc” interpolation.

Returns:

out_img – A 2D numpy array containing the resampled image data.

Return type:

2D numpy.ndarray