understanding render_curved

[rohitsaluja22]

Hey I am trying to understand function "def render_curved(self,font,word_text):" defined in text_utils.

I took a font "Shobhika" https://github.com/Sandhi-IITBombay/Shobhika
loaded it with the size of 30

font_file
'/home/rohit/.local/share/fonts/Shobhika-Regular.otf'
font = pygame.freetype.Font(font_file,30)
font
Font('/home/rohit/.local/share/fonts/Shobhika-Regular.otf')

Got a surface of size 134X159 accordingly for word_text = "hello":-

word_text = "hello"
wl = len(word_text) # = 5
lspace = font.get_sized_height() + 1
lspace
53
lbound = font.get_rect(word_text)
lbound
<rect(0, 23, 67, 23)>
fsize = (round(2lbound.width), round(3lspace))
fsize
(134, 159)
surf = pygame.Surface(fsize, pygame.SRCALPHA, 32)
surf
<Surface(134x159x32 SW)>

Got the following curve and rots as samples:-

mid_idx = wl//2
BS = self.baselinestate.get_sample()
curve = [BS'curve' for i in range(wl)]
curve[mid_idx] = -np.sum(curve) / (wl-1)
rots = [-int(math.degrees(math.atan(BS'diff'/(font.size/2)))) for i in range(wl)]
curve
[-1.75256073377731, -0.4381401834443275, 1.0953504586108187, -0.4381401834443275, -1.75256073377731]
rots
[-6, -3, 0, 3, 6]

The following code of updating rect.centerx is clear:-

bbs = []
rect = font.get_rect(word_text)
rect
<rect(0, 23, 67, 23)>
surf.get_rect().centerx
67
rect.centerx = surf.get_rect().centerx
rect
<rect(34, 23, 67, 23)>

It seems like (0,23) was the left bottom point WITH CO-ORDINATE SYSTM OF IMAGE X GOING RIGHT Y GOING DOWN, which got shifted to (34,23) i.e. centre(67) - rendered_word_text_width//2(i.e. 67//2 = 33) = 34

Now, the problem is in understanding the update of rect.centery:-

rect.centery
34
surf.get_rect().centery
79
rect.height
23
rect
<rect(34, 23, 67, 23)>
rect.centery = surf.get_rect().centery + rect.height
rect
<rect(34, 91, 67, 23)>

centery of rect is moved to 79 + 23 i.e 102, so the bottom point should be 102 + 23//2 = 113 but what we get is 91. Can you explain?

Also in function place_text: why is loc, which is the random choice of x and y coordinates from the collision-free location in the mask, reversed as loc[::-1] while updating bounding boxes bbs[i] = move_bb(bbs[i],loc[::-1]) ?

[ankush-me]

@rohitsaluja22:
(1) the bottom point should be (center - h/2) = 102 - 23/2 = 91 -- which is what you get.
(2) Pygame surface is transposed wrt opencv / normal image conventions, hence, we need to reverse the coordinates.