Defines | |
#define | CPL_OPERATION CPL_IMAGE_WARP_POLYNOMIAL |
Warp an image according to a 2d polynomial transformation. | |
#define | CPL_OPERATION CPL_IMAGE_RESAMPLE_SUBSAMPLE |
Warp an image according to a 2d polynomial transformation. | |
Functions | |
cpl_image * | cpl_image_extract_subsample (const cpl_image *image, int llx, int lly, int urx, int ury, int xstep, int ystep) |
Sub-sample an image. | |
double | cpl_image_get_interpolated (const cpl_image *source, double xpos, double ypos, const cpl_vector *xprofile, double xradius, const cpl_vector *yprofile, double yradius, double *pconfid) |
Interpolate a pixel. |
#include "cpl_image_resample.h"
|
Warp an image according to a 2d polynomial transformation.
x = cpl_polynomial_eval(pu, (u, v)) y = cpl_polynomial_eval(pv, (u, v)) Attention! The polynomials define a reverse transform. (u,v) are coordinates in the warped image and (x,y) are coordinates in the original image. The transform you provide is used to compute from the warped image, which pixels contributed in the original image. FIXME: Flux-calibration is missing. FIXME: Not thoroughly tested. Beware that extreme transformations may lead to blank images. The input image type can be CPL_TYPE_INT, CPL_TYPE_FLOAT and CPL_TYPE_DOUBLE. The two images may have different dimensions and types. Possible _cpl_error_code_ set in this function:
|
|
Warp an image according to a 2d polynomial transformation.
x = cpl_polynomial_eval(pu, (u, v)) y = cpl_polynomial_eval(pv, (u, v)) Attention! The polynomials define a reverse transform. (u,v) are coordinates in the warped image and (x,y) are coordinates in the original image. The transform you provide is used to compute from the warped image, which pixels contributed in the original image. FIXME: Flux-calibration is missing. FIXME: Not thoroughly tested. Beware that extreme transformations may lead to blank images. The input image type can be CPL_TYPE_INT, CPL_TYPE_FLOAT and CPL_TYPE_DOUBLE. The two images may have different dimensions and types. Possible _cpl_error_code_ set in this function:
|
|
Sub-sample an image.
Currently xstep must equal ystep. Currently both llx and lly must equal 1. Currently both urx and ury must equal the X- and Y-size of the image. step represents the sampling step in x and y: a step of 2 will create an image with a qaurter of the pixels of the input image. Currently, both the X- and Y-size of the image must be divisible by the step. image type can be CPL_TYPE_INT, CPL_TYPE_FLOAT and CPL_TYPE_DOUBLE. The returned image must be deallocated using cpl_image_delete(). Possible _cpl_error_code_ set in this function:
|
|
Interpolate a pixel.
The radii are only required to be positive. However, for small radii, especially radii less than 1/sqrt(2), (xpos, ypos) may be located such that no source pixels are included in the interpolation, causing the interpolated pixel value to be undefined. The X- and Y-profiles can be generated with cpl_vector_fill_kernel_profile(profile, radius). For profiles generated with cpl_vector_fill_kernel_profile() it is important to use the same radius both there and in cpl_image_get_interpolated(). A good profile length is CPL_KERNEL_DEF_SAMPLES, using radius CPL_KERNEL_DEF_WIDTH. On error *pconfid is negative (unless pconfid is NULL). Otherwise, if *pconfid is zero, the interpolated pixel-value is undefined. Otherwise, if *pconfid is less than 1, the area of inclusion is close to the image border or contains rejected pixels. The input image type can be CPL_TYPE_INT, CPL_TYPE_FLOAT and CPL_TYPE_DOUBLE. Here is an example of a simple image unwarping (with error-checking omitted for brevity): const double xyradius = CPL_KERNEL_DEF_WIDTH; cpl_vector * xyprofile = cpl_vector_new(CPL_KERNEL_DEF_SAMPLES); cpl_image * unwarped = cpl_image_new(nx, ny, CPL_TYPE_DOUBLE); cpl_vector_fill_kernel_profile(xyprofile, CPL_KERNEL_DEFAULT, xyradius); for (iu = 1; iu <= nx; iu++) { for (iv = 1; iv <= ny; iv++) { double confidence; const double x = my_unwarped_x(); const double y = my_unwarped_y(); const double value = cpl_image_get_interpolated(warped, x, y, xyprofile, xyradius, xyprofile, xyradius, &confidence); if (confidence > 0) cpl_image_set(unwarped, iu, iv, value); else cpl_image_reject(unwarped, iu, iv); } } cpl_vector_delete(xyprofile); Possible _cpl_error_code_ set in this function:
|