Common Image Drawing Routines Explained#
Overview#
OpenMV is a small embedded machine vision module widely used for rapid development of computer vision applications. OpenMV’s image drawing methods can be used to draw various shapes and text on images for visual feedback and debugging.
CanMV supports OpenMV image drawing methods, and adds some, such as drawing Chinese character strings draw_string_advanced
Common Functions#
draw_string_advanced#
The draw_string_advanced function uses freetype to render text, supports Chinese, and allows users to specify the font.
Syntax
image.draw_string_advanced(x,y,char_size,str,[color, font])
Parameter Explanation
x, y: Starting coordinates.char_size: Character sizestr: Chinese characters to be drawncolor: Text color.font: Font file path
Example
img.draw_string_advanced(10, 10, 32, "你好世界", color=(255, 0, 0)) # 绘制红色线
draw_line#
The draw_line function can draw a line on an image.
Syntax
image.draw_line(x0, y0, x1, y1, color)
Parameter Explanation
x0, y0: Starting coordinates.x1, y1: Ending coordinates.color: Line color.
Example
img.draw_line(10, 10, 100, 100, color=(255, 0, 0)) # 绘制红色线
draw_rectangle#
The draw_rectangle function can draw a rectangle on an image.
Syntax
image.draw_rectangle(x, y, w, h, color, thickness=1)
Parameter Explanation
x, y: Upper-left corner coordinates of the rectangle.w, h: Width and height of the rectangle.color: Color of the rectangle.thickness: Border thickness of the rectangle (default is 1).
Example
img.draw_rectangle(20, 20, 50, 30, color=(0, 255, 0), thickness=2) # 绘制绿色矩形
draw_circle#
The draw_circle function can draw a circle on an image.
Syntax
image.draw_circle(x, y, r, color, thickness=1)
Parameter Explanation
x, y: Circle center coordinates.r: Radius of the circle.color: Color of the circle.thickness: Border thickness of the circle (default is 1).
Example
img.draw_circle(60, 60, 30, color=(0, 0, 255), thickness=3) # 绘制蓝色圆
draw_cross#
The draw_cross function can draw a cross on an image.
Syntax
image.draw_cross(x, y, color, size=5, thickness=1)
Parameter Explanation
x, y: Cross point coordinates.color: Color of the cross.size: Size of the cross (default is 5).thickness: Line thickness of the cross (default is 1).
Example
img.draw_cross(40, 40, color=(255, 255, 0), size=10, thickness=2) # 绘制黄色交叉
draw_arrow#
The draw_arrow function can draw an arrow line on an image.
Syntax
image.draw_arrow(x0, y0, x1, y1, color, thickness=1)
Parameter Explanation
x0, y0: Starting coordinates.x1, y1: Ending coordinates.color: Color of the arrow.thickness: Line thickness of the arrow (default is 1).
Example
img.draw_arrow(10, 10, 100, 100, color=(255, 0, 0), thickness=2) # 绘制红色箭头
draw_ellipse#
The draw_ellipse function can draw an ellipse on an image.
Syntax
image.draw_ellipse(cx, cy, rx, ry, color, thickness=1)
Parameter Explanation
cx, cy: Coordinates of the ellipse center.rx, ry: Radii of the ellipse (x-axis and y-axis directions).color: Color of the ellipse.thickness: Border thickness of the ellipse (default is 1).
Example
img.draw_ellipse(60, 60, 30, 20, color=(0, 0, 255), thickness=3) # 绘制蓝色椭圆
draw_image#
The draw_image function can draw another image on the current image.
Syntax
image.draw_image(img, x, y, alpha=128, scale=1.0)
Parameter Explanation
img: The image object to be drawn.x, y: Upper-left corner coordinates of the drawing position.alpha: Transparency (0-256).scale: Scale ratio (default is 1.0).
Example
overlay = image.Image("overlay.bmp")
img.draw_image(overlay, 10, 10, alpha=128, scale=1.0) # 在(10, 10)位置绘制 overlay.bmp
draw_keypoints#
The draw_keypoints function can draw keypoints on an image.
Syntax
image.draw_keypoints(keypoints, size=10, color, thickness=1)
Parameter Explanation
keypoints: List of keypoints, each keypoint is an (x, y) tuple.size: Size of the keypoints (default is 10).color: Color of the keypoints.thickness: Border thickness of the keypoints (default is 1).
Example
keypoints = [(30, 30), (50, 50), (70, 70)]
img.draw_keypoints(keypoints, size=10, color=(255, 255, 0), thickness=2) # 绘制黄色关键点
flood_fill#
The flood_fill function can perform a flood fill algorithm on an image, starting from the specified starting point and filling with the specified color.
Syntax
image.flood_fill(x, y, color, threshold, invert=False, clear_background=False)
Parameter Explanation
x, y: Starting point coordinates.color: Fill color.threshold: Fill threshold, indicating the allowed color difference range between the starting pixel and adjacent pixels.invert: Boolean value, if True, reverses the fill condition.clear_background: Boolean value, if True, clears the background outside the fill area.
Example
img.flood_fill(30, 30, color=(255, 0, 0), threshold=30, invert=False, clear_background=False) # 从(30, 30)开始填充红色
draw_string#
The draw_string function can draw a string on an image.
Syntax
image.draw_string(x, y, text, color, scale=1)
Parameter Explanation
x, y: Starting coordinates of the string.text: String content to be drawn.color: Color of the string.scale: Scale ratio of the string (default is 1).
Example
img.draw_string(10, 10, "Hello OpenMV", color=(255, 255, 255), scale=2) # 绘制白色字符串
Example#
This example is for feature demonstration only
import time, os, gc, sys, urandom
from media.display import *
from media.media import *
DISPLAY_IS_HDMI = False
DISPLAY_IS_LCD = True
DISPLAY_IS_IDE = False
try:
# 设置默认大小
width = 640
height = 480
if DISPLAY_IS_HDMI:
# 使用HDMI作为显示输出，设置1080P
Display.init(Display.LT9611, width = 1920, height = 1080, to_ide = True)
width = 1920
height = 1080
elif DISPLAY_IS_LCD:
# 使用LCD作为显示输出
Display.init(Display.ST7701, width = 800, height = 480, to_ide = True)
width = 800
height = 480
elif DISPLAY_IS_IDE:
# 使用IDE作为显示输出
Display.init(Display.VIRT, width = 800, height = 480, fps = 100)
width = 800
height = 480
else:
raise ValueError("Shoule select a display.")
# 初始化媒体管理器
MediaManager.init()
fps = time.clock()
# 创建绘制的图像
img = image.Image(width, height, image.ARGB8888)
while True:
fps.tick()
# 检查是否在退出点
os.exitpoint()
img.clear()
# 绘制红色线
img.draw_line(10, 10, 100, 100, color=(255, 0, 0))
# 绘制绿色矩形
img.draw_rectangle(20, 20, 50, 30, color=(0, 255, 0), thickness=2)
# 绘制蓝色圆
img.draw_circle(30, 30, 30, color=(0, 0, 255), thickness=3)
# 绘制黄色交叉
img.draw_cross(40, 40, color=(255, 255, 0), size=10, thickness=2)
# 绘制红色字符串
img.draw_string_advanced(50, 50, 32, "你好世界", color=(255, 0, 0))
# 绘制白色字符串
img.draw_string_advanced(50, 100, 32, "Hello CanMV", color=(255, 255, 255), scale=2)
# 绘制红色箭头
img.draw_arrow(60, 60, 100, 100, color=(255, 0, 0), thickness=2)
# 绘制蓝色椭圆
radius_x = urandom.getrandbits(30) % (max(img.height(), img.width())//2)
radius_y = urandom.getrandbits(30) % (max(img.height(), img.width())//2)
rot = urandom.getrandbits(30)
img.draw_ellipse(70, 70, radius_x, radius_y, rot, color = (0, 0, 255), thickness = 2, fill = False)
# 绘制另一个图像
# overlay = image.Image("overlay.bmp")
# img.draw_image(overlay, 10, 10, alpha=128, scale=1.0)
# 绘制黄色关键点
keypoints = [(30, 30), (50, 50), (70, 70)]
img.draw_keypoints([(30, 40, rot)], color = (255, 255, 0), size = 20, thickness = 2, fill = False)
# 执行洪水填充
img.flood_fill(90, 90, color=(255, 0, 0), threshold=30, invert=False, clear_background=False)
# 显示绘制结果
Display.show_image(img)
#print(fps.fps())
time.sleep_ms(10)
except KeyboardInterrupt as e:
print(f"user stop")
except BaseException as e:
print(f"Exception '{e}'")
finally:
# 销毁 display
Display.deinit()
os.exitpoint(os.EXITPOINT_ENABLE_SLEEP)
time.sleep_ms(100)
# 释放媒体缓冲区
MediaManager.deinit()
Tip
For specific interface definitions, please refer to image