¶ jpg_decode method
jpg_decode(jpg_filename {, x, y, width, height})
Decode a jpg file and return it or a portion of it as a tuple composed of (buffer, width, height). The buffer is a color565 blit_buffer compatible byte array. The buffer will require width * height * 2 bytes of memory.
If the optional x, y, width, and height parameters are given, the buffer will only contain the specified area of the image.
¶ blit_buffer method
blit_buffer(buffer, x, y, width, height {, alpha})
Copy bytes() or bytearray() content to the screen internal memory, x, y, width, height specified area. Note: every color requires 2 bytes in the array. alpha defaults to 255.
¶ Refresh the specified area of JPG
Based on Make semi-transparent rectangular text box , rewrite the text_rect method as a class and add an erase method, in which you use the jpg_decode method to store the semi-transparent text box background, then use the blit_buffer method to overwrite the semi-transparent text box, achieving partial refresh.
""" BPI-Centi-S3 170x320 ST7789 display """
import st7789
import vga1_bold_16x32
import tft_config
import gc
import time
class TextRect:
def __init__(self):
self.tft = None
self.text_y = None
self.text_x = None
self.rect_height = None
self.rect_width = None
def rect(self, tft, font, text, text_coord,
fg=st7789.WHITE, bg=st7789.BLACK, alpha_text=255, alpha_rect=255):
self.tft = tft
self.rect_width = font.WIDTH * len(text)
self.rect_height = font.HEIGHT
self.text_x = text_coord[0]
self.text_y = text_coord[1]
self.tft.fill_rect(self.text_x, self.text_y,
self.rect_width, self.rect_height, bg, alpha_rect)
self.tft.text(font, text, self.text_x, self.text_y,
fg, st7789.TRANSPARENT, alpha_text)
def erase(self, bg):
buffer, _, _ = self.tft.jpg_decode(bg, self.text_x, self.text_y, self.rect_width, self.rect_height)
self.tft.blit_buffer(buffer, self.text_x, self.text_y, self.rect_width, self.rect_height)
def main():
try:
text_x = 10
text_y = int(170 / 2 - 32)
tft = tft_config.config(rotation=1)
jpg = 'pic_6.jpg'
text_list = [
"This Is Just To Say",
"I have eaten",
"the plums",
"that were in",
"the icebox",
"and which",
"you were probably",
"saving",
"for breakfast",
"Forgive me",
"they were delicious",
"so sweet",
"and so cold"]
tft.init()
gc.collect()
tft.jpg(jpg, 0, 0)
text_rect_1 = TextRect()
while True:
for i in text_list:
text_rect_1.rect(tft, vga1_bold_16x32, i, (text_x, text_y),
fg=st7789.YELLOW, bg=st7789.BLACK, alpha_text=30, alpha_rect=80)
tft.show()
time.sleep(0.5)
text_rect_1.erase(bg=jpg)
gc.collect()
except BaseException as err:
err_type = err.__class__.__name__
print('Err type:', err_type)
from sys import print_exception
print_exception(err)
finally:
tft.deinit()
print("tft deinit")
main()