POLYWARP Procedure

Standard Library procedure that calculates the coefficients needed for a polynomial image warping transformation.

NOTE: The xm (x-coefficients) and ym (y-coefficients) can be used as input for the POLY_2D function. POLY_2D performs the actual warping of the image, using the x and y transformation coefficients that you provide.

Example

image = BYTSCL(DIST(300))
WINDOW, XSize=300, YSize=300
TV, image

; Create a test image and display it.

xin = [100, 200, 200, 100]
yin = [200, 200, 100, 100]
XYOUTS, 100, 200, '0', /Device
XYOUTS, 200, 200, '1', /Device
XYOUTS, 200, 100, '2', /Device
XYOUTS, 100, 100, '3', /Device

; Create arrays describing four independent control points and plot
; these points on top of the image. These points describe a square,
; and represent the position of points in a calibration image.

xd = INTARR(4)
yd = INTARR(4)
FOR i=0,3 DO BEGIN

PRINT, 'Pick warped point ', i
CURSOR, xt, yt, /Device
WAIT, 0.5
xd(i) = xt
yd(i) = yt

ENDFOR

; Pick four dependent warping control points from the image; these
; points represent the calibration points as actually measured by an
; instrument, which, due to distortion, has warped them.

deg = 1
POLYWARP, xd, yd, xin, yin, deg, xm, ym

; Perform linear (first degree) warping. POLYWARP will return xm
; and ym, the coefficients of the polynomial functions which describes
; this warping.

interp = 1
result = POLY_2D(image, xm, ym, interp)

; Apply the polynomial functions calculated with POLYWARP to the
; first image, using bilinear interpolation.

TVSCL, result

; Display the resulting image, which represents the image after
; correcting for instrument distortion.

POLYWARP Procedure

Usage

Input Parameters

Output Parameters

Keywords

Discussion

Example

See Also