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在固定阈值二值化中#xff0c;像素值根据一个预定义的阈值进行分类#xff0c;大于阈值的…目录

1.固定值二值化

固定阈值二值化是OpenCV中一种简单而常用的图像处理技术用于将图像转换为二值图像。

在固定阈值二值化中像素值根据一个预定义的阈值进行分类大于阈值的像素被设置为白色而小于或等于阈值的像素被设置为黑色。

以下是关于OpenCV固定阈值二值化的一些重要知识点

threshold()

src输入图像通常为灰度图像。

dst输出二值图像与输入图像具有相同的大小和类型。

thresh固定阈值用于将像素分类为黑色或白色。

maxValue分配给大于阈值的像素的像素值。

thresholdType阈值类型用于指定阈值化的方式如

THRESH_BINARY、THRESH_BINARY_INV

2.阈值类型使用

参数可以选择不同的固定阈值化类型以满足特定需求。

一些常用的阈值类型包括

0。

THRESH_BINARY_INV反二进制阈值化大于阈值的像素值设为

maxValue。

THRESH_TRUNC截断阈值化大于阈值的像素值设为阈值小于等于阈值的保持不变。

THRESH_TOZERO截断到零阈值化大于阈值的像素值保持不变小于等于阈值的像素值设为

0。

THRESH_TOZERO_INV反截断到零阈值化大于阈值的像素值设为

3.例子

gray;cvtColor(image,gray,COLOR_BGR2GRAY);

灰度图像

img_B,img_B_V;threshold(image,img_B,125,255,THRESH_BINARY);imwrite(/sdcard/DCIM/img_B.png,img_B);3.灰度图BINARY二值化

Mat

gray_B,gray_B_V;threshold(gray,gray_B,125,255,THRESH_BINARY);threshold(gray,gray_B_V,125,255,THRESH_BINARY_INV);imwrite(/sdcard/DCIM/gray_B.png,gray_B);imwrite(/sdcard/DCIM/gray_B_V.png,gray_B_V);

gray_B

gray_T,gray_T_V;threshold(gray,gray_T,125,255,THRESH_TOZERO);threshold(gray,gray_T_V,125,255,THRESH_TOZERO_INV);imwrite(/sdcard/DCIM/gray_T.png,gray_T);imwrite(/sdcard/DCIM/gray_T_V.png,gray_T_V);

gray_T

gray_TRUNC;threshold(gray,gray_TRUNC,125,255,THRESH_TRUNC);imwrite(/sdcard/DCIM/gray_TRUNC.png,gray_TRUNC);

gray_TRUNC

img_Thr;cvtColor(image,img_Thr,COLOR_BGR2GRAY);Mat

img_Thr_0,img_Thr_T;threshold(img_Thr,img_Thr_0,100,255,THRESH_BINARY|cv::THRESH_OTSU);threshold(img_Thr,img_Thr_T,125,255,THRESH_BINARY|cv::THRESH_TRIANGLE);imwrite(/sdcard/DCIM/img_Thr_0.png,img_Thr_0);imwrite(/sdcard/DCIM/img_Thr_T.png,img_Thr_T);

img_Thr_T

src输入图像通常为灰度图像。

dst输出二值图像与输入图像具有相同的大小和类型。

maxValue分配给超过阈值的像素的像素值。

adaptiveMethod自适应阈值化方法用于指定计算局部阈值的方式可以是

ADAPTIVE_THRESH_GAUSSIAN_C。

thresholdType阈值化类型用于指定阈值化的方式如

THRESH_BINARY、THRESH_BINARY_INV

等。

blockSize用于计算局部阈值的像素领域大小。

必须是奇数且大于1。

C从计算阈值中减去的常数。

通常为正值。

2.自适应阈值化方法使用

参数可以选择不同的自适应阈值化方法以满足特定需求。

在OpenCV中常见的自适应阈值化方法有两种

ADAPTIVE_THRESH_MEAN_C根据领域中像素的均值计算局部阈值。

ADAPTIVE_THRESH_GAUSSIAN_C根据领域中像素的加权和权重为高斯窗口计算局部阈值。

3.灰度图像转换在进行自适应阈值二值化之前要将彩色图像转换为灰度图像。

可以使用

cvtColor()

cvtColor(image,img_Thr,COLOR_BGR2GRAY);

4.例子

adaptiveThreshold(img_Thr,adaptive_mean,255,ADAPTIVE_THRESH_MEAN_C,THRESH_BINARY,55,0);

adaptiveThreshold(img_Thr,adaptive_gauss,255,ADAPTIVE_THRESH_GAUSSIAN_C,THRESH_BINARY,55,0);

imwrite(/sdcard/DCIM/adaptive_mean.png,adaptive_mean);

imwrite(/sdcard/DCIM/adaptive_gauss.png,adaptive_gauss);

adaptive_gauss

__android_log_print(ANDROID_LOG_DEBUG,

LOG_TAG,

Java_com_example_myapplication_MainActivity_opencv_1test(JNIEnv

*env,

*pixels;CV_Assert(AndroidBitmap_getInfo(env,

bitmap,

、RGBA_8888CV_Assert(info.format

ANDROID_BITMAP_FORMAT_RGBA_8888

||info.format

ANDROID_BITMAP_FORMAT_RGB_565);CV_Assert(AndroidBitmap_lockPixels(env,

bitmap,

0);CV_Assert(pixels);//将bitmap转化为Mat类Mat

image(info.height,

gray;cvtColor(image,gray,COLOR_BGR2GRAY);imwrite(/sdcard/DCIM/gray23.png,gray);Mat

img_B,img_B_V,gray_B,gray_B_V,gray_T,gray_T_V,gray_TRUNC;//彩色图像二值化threshold(image,img_B,125,255,THRESH_BINARY);imwrite(/sdcard/DCIM/img_B.png,img_B);//灰度图BINARY二值化threshold(gray,gray_B,125,255,THRESH_BINARY);threshold(gray,gray_B_V,125,255,THRESH_BINARY_INV);imwrite(/sdcard/DCIM/gray_B.png,gray_B);imwrite(/sdcard/DCIM/gray_B_V.png,gray_B_V);//灰度图像TOZERO变换threshold(gray,gray_T,125,255,THRESH_TOZERO);threshold(gray,gray_T_V,125,255,THRESH_TOZERO_INV);imwrite(/sdcard/DCIM/gray_T.png,gray_T);imwrite(/sdcard/DCIM/gray_T_V.png,gray_T_V);//灰度图像TRUNC变换threshold(gray,gray_TRUNC,125,255,THRESH_TRUNC);imwrite(/sdcard/DCIM/gray_TRUNC.png,gray_TRUNC);//灰度图像大津法和三角形法二值化Mat

img_Thr;cvtColor(image,img_Thr,COLOR_BGR2GRAY);Mat

img_Thr_0,img_Thr_T;threshold(img_Thr,img_Thr_0,100,255,THRESH_BINARY|cv::THRESH_OTSU);threshold(img_Thr,img_Thr_T,125,255,THRESH_BINARY|cv::THRESH_TRIANGLE);imwrite(/sdcard/DCIM/img_Thr_0.png,img_Thr_0);imwrite(/sdcard/DCIM/img_Thr_T.png,img_Thr_T);Mat

adaptive_mean,adaptive_gauss;adaptiveThreshold(img_Thr,adaptive_mean,255,ADAPTIVE_THRESH_MEAN_C,THRESH_BINARY,55,0);adaptiveThreshold(img_Thr,adaptive_gauss,255,ADAPTIVE_THRESH_GAUSSIAN_C,THRESH_BINARY,55,0);imwrite(/sdcard/DCIM/adaptive_mean.png,adaptive_mean);imwrite(/sdcard/DCIM/adaptive_gauss.png,adaptive_gauss);