# Example code for:
# Gradient calculation (emboss) in the horizontal direction using a 
# super simple [-3,0,3] style filter.
#
# Jay Summet 2024
#
#Python 3.10, OpenCV 4.5.x
#

import cv2
import numpy as np

def scaleTo8Bit(image, displayMin = None, displayMax=None ):

   if displayMin == None:
       displayMin = np.min(image)

   if displayMax == None:
      displayMax = np.max(image)

   np.clip(image, displayMin, displayMax, out=image)

   image = image - displayMin
   cf = 255. / (displayMax - displayMin)
   imageOut = ( cf * image).astype(np.uint8)

   return imageOut





#Load source / input image as grayscale, also works on color images...
imgIn = cv2.imread("blueSky.jpg", cv2.IMREAD_GRAYSCALE)
cv2.imshow("Original", imgIn)

#Convert to floating point so our output of filter2D will also be floating
#point image. (To preserve full 255...0...-255 range.)
imgIn = imgIn.astype(np.float32)

#Create the  filter
kernel = np.zeros( (1,2), np.float32)
kernel[0,0] = -3.0	#Try 2.0
kernel[0,1] = 3.0 	#Try 2.0

#A square  filter you can also try...
#kernel = np.zeros( (3,3), np.float32)
#kernel[1,0] = -0.5	#Try -1.5
#kernel[1,2] = 0.5	#Try 1.5


#Do the actual kernel operation...
output = cv2.filter2D(imgIn, -1, kernel)

cv2.imshow("not scaled", output)
#cv2.imwrite("incorrect-scaling-example.png", output)
#Scaling back so that the zero point is at 128 (gray)...
output8bit = scaleTo8Bit(output)
cv2.imshow("Emboss H", output8bit)


cv2.waitKey(0)
cv2.startWindowThread()