Question

我正在使用下面的代码来检测面孔：

import io
import picamera
import cv2
import numpy
import PIL
from PIL import Image
from resizeimage import resizeimage

#Load a cascade file for detecting faces
face_cascade = cv2.CascadeClassifier('/usr/share/opencv/haarcascades/haarcascade_frontalface_alt.xml')

#Create a memory stream so photos doesn't need to be saved in a file
stream = io.BytesIO()

#Get the picture (low resolution, so it should be quite fast)
#Here you can also specify other parameters (e.g.:rotate the image)
with picamera.PiCamera() as camera:
    camera.resolution = (640, 480)
    camera.vflip = False
    camera.hflip = False
    camera.brightness = 60
    camera.capture(stream, format='jpeg')

#Convert the picture into a numpy array
buff = numpy.fromstring(stream.getvalue(), dtype=numpy.uint8)

#Now creates an OpenCV image
image = cv2.imdecode(buff, 1)

#Load a cascade file for detecting faces
#face_cascade = cv2.CascadeClassifier('/usr/share/opencv/haarcascades/haarcascade_frontalface_alt.xml')

#Convert to grayscale
gray = cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)

#Look for faces in the image using the loaded cascade file
faces = face_cascade.detectMultiScale(gray, 1.1, 5)

print "Found "+str(len(faces))+" face(s)"

#Draw a rectangle around every found face
#Crop faces and save to separate files
id = 1
for (x,y,w,h) in faces:
    cv2.rectangle(image,(x,y),(x+w,y+h),(255,0,0),2)
    cropped = image[ y : y+h, x : x+w ]
    #RESIZE IMAGE to 92x112
    cropped = cv2.resize(cropped,None,92,112)
    cv2.imwrite("../reco/test_faces/cropped_face" + str(id) + ".png", cropped)
    id = id + 1

最后，我想将面部裁剪成图像文件，并将它们调整为92x112。这就是我尝试的方法

cropped = cv2.resize(cropped,None,92,112)

当我跑步时，我得到了

OpenCV错误：在调整大小时，断言失败（dsize.area（）||（inv_scale_x＆gt; 0＆amp;＆amp; inv_scale_y＆gt; 0）），文件/build/opencv-ISmtkH/opencv-2.4.9.1+dfsg/ modules / imgproc / src / imgwarp.cpp，第1835行 Traceback（最近一次调用最后一次）：文件“1track.py”，第48行，in cropped = cv2.resize（cropped，None，92,112） cv2.error：/build/opencv-ISmtkH/opencv-2.4.9.1+dfsg/modules/imgproc/src/imgwarp.cpp:1835：错误：（-215）dsize.area（）||函数调整大小（inv_scale_x＆gt; 0＆amp;＆amp; inv_scale_y＆gt; 0）

任何帮助都会很棒。对不起，如果这个问题是愚蠢的，我是编程的绝对初学者，上面的代码是一个谷歌搜索结果.. 谢谢！

Answer 1

要将图像调整为新尺寸，您需要知道新尺寸与当前尺寸之间的比率。因此，如果您想将（例如）640x480图像设置为92x112图像：

六百四十○分之九十二= 0.143 四百八十零分之一百十二= 0.233

您可以在cv2.resize函数中使用这些比率：

cropped = cv2.resize(cropped, (0,0), fx=0.143, fy=0.233)

Python - 调整图像大小

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