find_blobs函數：
通過find_blobs函數可以找到色塊.我們來討論一下，find_blobs的細節。
image.find_blobs(thresholds, roi=Auto, x_stride=2, y_stride=1, invert=False, area_threshold=10, pixels_threshold=10, merge=False, margin=0, threshold_cb=None, merge_cb=None)
這里的參數比較多。
- thresholds是顏色的閾值，注意：這個參數是一個列表，可以包含多個顏色。如果你只需要一個顏色，那么在這個列表中只需要有一個顏色值，如果你想要多個顏色閾值，那這個列表就需要多個顏色閾值。注意：在返回的色塊對象blob可以調用code方法，來判斷是什么顏色的色塊。
-
red = (xxx,xxx,xxx,xxx,xxx,xxx) blue = (xxx,xxx,xxx,xxx,xxx,xxx) yellow = (xxx,xxx,xxx,xxx,xxx,xxx) img=sensor.snapshot() red_blobs = img.find_blobs([red]) color_blobs = img.find_blobs([red,blue, yellow])
-
roi是“感興趣區”。
left_roi = [0,0,160,240]
blobs = img.find_blobs([red],roi=left_roi) -
x_stride 就是查找的色塊的x方向上最小寬度的像素，默認為2，如果你只想查找寬度10個像素以上的色塊，那么就設置這個參數為10：
blobs = img.find_blobs([red],x_stride=10)
-
y_stride 就是查找的色塊的y方向上最小寬度的像素，默認為1，如果你只想查找寬度5個像素以上的色塊，那么就設置這個參數為5：
blobs = img.find_blobs([red],y_stride=5)
- invert 反轉閾值，把閾值以外的顏色作為閾值進行查找
- area_threshold 面積閾值，如果色塊被框起來的面積小於這個值，會被過濾掉
- pixels_threshold 像素個數閾值，如果色塊像素數量小於這個值，會被過濾掉
- merge 合並，如果設置為True，那么合並所有重疊的blob為一個。
注意：這會合並所有的blob，無論是什么顏色的。如果你想混淆多種顏色的blob，只需要分別調用不同顏色閾值的find_blobs。 -
all_blobs = img.find_blobs([red,blue,yellow],merge=True) red_blobs = img.find_blobs([red],merge=True) blue_blobs = img.find_blobs([blue],merge=True) yellow_blobs = img.find_blobs([yellow],merge=True)
- margin 邊界，如果設置為1，那么兩個blobs如果間距1一個像素點，也會被合並。
閾值：
一個顏色閾值的結構是這樣的：
red = (minL, maxL, minA, maxA, minB, maxB)
元組里面的數值分別是L A B 的最大值和最小值。
顏色閾值選擇工具：
OpenMV 的IDE里加入了閾值選擇工具，極大的方便了對於顏色閾值的調試。
首先運行hello world.py讓IDE里的framebuffer顯示圖案。
然后打開 工具 →機器視覺 → 閾值編譯器
點擊 Frame Buffer可以獲取IDE中的圖像，Image File可以自己選擇一個圖像文件。
拖動六個滑塊，可以實時的看到閾值的結果，我們想要的結果就是，將我們的目標顏色變成白色，其他顏色全變為黑色。
單顏色識別之紅色：
import sensor, image, time
#thresholds = [(66, 0, -51, -8, 6, 127)] #green
thresholds = [(30, 100, 15, 127, 15, 127)] #red
#thresholds = [(66, 0, -51, -8, 6, 127),(30, 100, 15, 127, 15, 127)] #元組里面,包含列表,進行多種顏色識別
sensor.reset() # Reset and initialize the sensor.
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QVGA) # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000) # Wait for settings take effect.
sensor.set_auto_gain(False)
sensor.set_auto_whitebal(False) #關掉白平衡和自動增益
clock = time.clock() # Create a clock object to track the FPS.
while(True):
clock.tick() # Update the FPS clock.
img = sensor.snapshot() # Take a picture and return the image.
#for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200,merge=True):
#for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200):
for blob in img.find_blobs([thresholds[0]],pixels_threshold=200,area_threshold=200):
img.draw_rectangle(blob.rect())
img.draw_cross(blob.cx(),blob.cy())
print(clock.fps()) # Note: OpenMV Cam runs about half as fast when connecte
現象：
單顏色識別之綠色：
import sensor, image, time
thresholds = [(66, 0, -51, -8, 6, 127)] #green
#thresholds = [(30, 100, 15, 127, 15, 127)] #red
#thresholds = [(66, 0, -51, -8, 6, 127),(30, 100, 15, 127, 15, 127)] #元組里面,包含列表,進行多種顏色識別
sensor.reset() # Reset and initialize the sensor.
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QVGA) # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000) # Wait for settings take effect.
sensor.set_auto_gain(False)
sensor.set_auto_whitebal(False) #關掉白平衡和自動增益
clock = time.clock() # Create a clock object to track the FPS.
while(True):
clock.tick() # Update the FPS clock.
img = sensor.snapshot() # Take a picture and return the image.
#for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200,merge=True):
#for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200):
for blob in img.find_blobs([thresholds[0]],pixels_threshold=200,area_threshold=200):
img.draw_rectangle(blob.rect())
img.draw_cross(blob.cx(),blob.cy())
print(clock.fps()) # Note: OpenMV Cam runs about half as fast when connected
現象：
多顏色識別之合並：
import sensor, image, time
#thresholds = [(66, 0, -51, -8, 6, 127)] #green
#thresholds = [(30, 100, 15, 127, 15, 127)] #red
thresholds = [(66, 0, -51, -8, 6, 127),(30, 100, 15, 127, 15, 127)] #元組里面,包含列表,進行多種顏色識別
sensor.reset() # Reset and initialize the sensor.
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QVGA) # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000) # Wait for settings take effect.
sensor.set_auto_gain(False)
sensor.set_auto_whitebal(False) #關掉白平衡和自動增益
clock = time.clock() # Create a clock object to track the FPS.
while(True):
clock.tick() # Update the FPS clock.
img = sensor.snapshot() # Take a picture and return the image.
for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200,merge=True):
#for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200):
#for blob in img.find_blobs([thresholds[0]],pixels_threshold=200,area_threshold=200):
img.draw_rectangle(blob.rect())
img.draw_cross(blob.cx(),blob.cy())
print(clock.fps()) # Note: OpenMV Cam runs about half as fast when connected
現象：
多顏色識別之不合並：
import sensor, image, time
#thresholds = [(66, 0, -51, -8, 6, 127)] #green
#thresholds = [(30, 100, 15, 127, 15, 127)] #red
thresholds = [(66, 0, -51, -8, 6, 127),(30, 100, 15, 127, 15, 127)] #元組里面,包含列表,進行多種顏色識別
sensor.reset() # Reset and initialize the sensor.
sensor.set_pixformat(sensor.RGB565) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QVGA) # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000) # Wait for settings take effect.
sensor.set_auto_gain(False)
sensor.set_auto_whitebal(False) #關掉白平衡和自動增益
clock = time.clock() # Create a clock object to track the FPS.
while(True):
clock.tick() # Update the FPS clock.
img = sensor.snapshot() # Take a picture and return the image.
#for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200,merge=True):
for blob in img.find_blobs(thresholds,pixels_threshold=200,area_threshold=200):
#for blob in img.find_blobs([thresholds[0]],pixels_threshold=200,area_threshold=200):
img.draw_rectangle(blob.rect())
img.draw_cross(blob.cx(),blob.cy())
print(clock.fps()) # Note: OpenMV Cam runs about half as fast when connected
現象：
正是步行者，一步步登峰！