使用python kivy+opencv实现手写数字识别的安卓app。
app下载：
https://pan.baidu.com/s/1l1iqMYmZeHuq-c_mg15F0Q
提取码：lvev

如有问题，欢迎下方评论！

代码部分：

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.graphics.texture import Texture
from kivy.uix.camera import Camera
from kivy.uix.image import Image
from kivy.uix.button import Button
from kivy.clock import Clock
from kivy.graphics import Color,Rectangle
import numpy as np
import cv2
from android.permissions import request_permissions, Permission

request_permissions([
    Permission.CAMERA,
    Permission.WRITE_EXTERNAL_STORAGE,
    Permission.READ_EXTERNAL_STORAGE
])


net = cv2.dnn.readNetFromTensorflow('model.pb')
def detect(src,net):

    try:
        src_copy=src.copy()
        gray=cv2.cvtColor(src,cv2.COLOR_RGB2GRAY)
        # thred=np.where(gray>140,255,0).astype('uint8')
        _,thred=cv2.threshold(gray,100,255,cv2.THRESH_BINARY_INV)
        # thred=255-thred
        #开闭运算
        k = np.ones((5, 5), np.uint8)
        #thred=cv.dilate(thred,k)
        thred = cv2.morphologyEx(thred, cv2.MORPH_CLOSE, k)
        thred=cv2.dilate(thred,k)
        # cv2.imshow('a123', thred)
        # cv2.waitKey(0)

        cnts=cv2.findContours(thred,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)[0]
        # print('轮廓数=',len(cnts))
        if len(cnts)>100:
            return src_copy,thred
        nam=[]
        for i in cnts:
            area = cv2.contourArea(i)
            if area<50:
                continue
            # if aa!=1:
            #     b=20
            # else:b=15
            # print('面积=',area)
            b=50
            if area>=b:
                x, y, w, h = cv2.boundingRect(i)

                x2=x-10
                y2=y-10
                w2=w+20
                h2=h+20
                cv2.rectangle(src_copy,(x2,y2),(x2+w2,y2+h2),(0,255,0),2)
                lkuo=thred[y:y+h,x:x+w]

                da = max(h, w)
                rate = da / 40
                ro = cv2.resize(lkuo, (int(w / rate), int(h / rate)))

                h, w = ro.shape
                t, b = int((43 - h) / 2), 43 - h - int((43 - h) / 2)
                l, r = int((43 - w) / 2), 43 - w - int((43 - w) / 2)

                ro = cv2.copyMakeBorder(ro, t, b, l, r, cv2.BORDER_CONSTANT, value=0)

                ro = cv2.resize(ro, (40, 40))
                ro = np.where(ro > 0, 255, 0).astype('float32')

                # cv.imshow('a123', ro)
                # cv.waitKey(0)

                ro = ro / 255
                # ro=np.reshape(ro,(1,40,40,1))

                blob=ro.reshape((1,1,40,40))
                net.setInput(blob)

                out=net.forward()
                #图上标出数字
                number=np.argmax(out,axis=-1)
                nam.append((number[0],x2, y2-5,h/40))
                #cv.putText(src_copy, str(number[0]), (x2, y2-5), cv.FONT_HERSHEY_SIMPLEX, h/40, (0, 0, 255), 2)

                #print('opencv预测结果：',np.argmax(out,axis=-1),'tensorflow预测结果：',np.argmax(out2,axis=-1))
        if len(nam)==0:
            return src_copy,thred

        for ii in nam:
            cv2.putText(src_copy, str(ii[0]), (ii[1], ii[2]), cv2.FONT_HERSHEY_SIMPLEX, ii[3], (0, 0, 255), 2)

        return src_copy,thred
    except:
        return src,src

class MyLayout(BoxLayout):
    def __init__(self):
        super(MyLayout, self).__init__()
        self.orientation='vertical'
        self.image1 = Image()
        self.image1.color=1,1,1,0
        self.image1.allow_stretch=True

        self.btn=Button(text='OPEN CAMERA')

        with self.canvas:
            Color(1,1,1,1)
            self.rect=Rectangle(pos=self.pos,size=self.size,source='11.jpg')
            self.bind(pos=self.update,size=self.update)

        self.padding=[0,0,0,10]
        self.spacing=10
        self.btn.size_hint=.3,.06
        self.btn.pos_hint={'center_x':0.5,'center_y':.5}
        self.btn.background_color=1,1,1,.8
        # self.btn.size_hint_y=.1
        # self.btn.size_hint_x=.2
        self.btn.bind(on_press=self.press_btn)

        self.camera = Camera(resolution=(640, 480))
        self.camera.play=False

        self.add_widget(self.image1)
        self.add_widget(self.btn)
        Clock.schedule_interval(self.pr, 0)
    def update(self,*args):
        self.rect.pos=self.pos
        self.rect.size=self.size
    def press_btn(self,arg):
        self.camera.play=not self.camera.play
        if self.camera.play:
            self.image1.color=1,1,1,1
            self.btn.text='CLOSE CAMERA'
        else:
            self.image1.color = 1, 1, 1, 0
            self.btn.text = 'OPEN CAMERA'
    def pr(self, nap):
        if self.camera.texture==None:

            return
        img_rgb=self.texture_to_numpy(self.camera.texture)[:,:,:3]

        img_rgb_90=np.rot90(img_rgb,-1)
        img_rgb_zy=img_rgb_90[:,::-1,:]

        out,_=detect(img_rgb_zy,net)
        #cv2.putText(img_rgba_copy, str(self.counter), (100, 100), cv2.FONT_HERSHEY_SIMPLEX, 2, (0, 255, 0), 3)#

        texture1=self.numpy_to_texture(out)
        self.image1.texture=texture1



    # 将Texture格式的图片对象转换为numpy
    def texture_to_numpy(self, data):
        image = np.asarray(bytearray(data.pixels), dtype='uint8').reshape((data.height, data.width, 4))
        # r_chanel = np.copy(image[:, :, 0])
        # g_chanel = np.copy(image[:, :, 1])
        # b_chanel = np.copy(image[:, :, 2])
        # image[:, :, 0] = b_chanel
        # image[:, :, 1] = g_chanel
        # image[:, :, 2] = r_chanel
        #返回rgba图像
        return image

    # 将numpy格式图片对象转为Texture
    def numpy_to_texture(self, frame):
        # frame=cv2.imread("ddd.jpg")
        buf1 = cv2.flip(frame, 0)
        buf = buf1.tostring()
        image_texture = Texture.create(size=(frame.shape[1], frame.shape[0]), colorfmt='rgb')
        image_texture.blit_buffer(buf, colorfmt='rgb', bufferfmt='ubyte')
        return image_texture


class MyApp(App):
    def build(self):



        return MyLayout()


if __name__ == '__main__':
    MyApp().run()