Java Opencv开山之路–(3)–Java Opencv 去除图片黑边

版权声明：编码不易，禁止转载 https://blog.csdn.net/u_ascend/article/details/85064795

利用opencv去除图片上下左右黑边。
代码：
类：ImageUtils.java

    /**
     * 去除图片黑边，若无黑边，则原图返回。默认“全黑”阈值为 {@code BLACK_VALUE}
     *
     * @param srcMat 预去除黑边的Mat
     * @return 去除黑边之后的Mat
     */
    public static Mat removeBlackEdge(Mat srcMat) {
        return removeBlackEdge(srcMat, BLACK_VALUE);
    }

    /**
     * 去除图片黑边，若无黑边，则原图返回。
     *
     * @param blackValue 一般低于5的已经是很黑的颜色了
     * @param srcMat     源Mat对象
     * @return Mat对象
     */
    public static Mat removeBlackEdge(Mat srcMat, int blackValue) {
        // 预截取，默认播放条等情况的处理
        Mat smallMat = cut(srcMat, (int) (srcMat.width() * 0.02), (int) (srcMat.height() * 0.02));
        // 灰度
        Mat grayMat = gray(smallMat);
        int topRow = 0;
        int leftCol = 0;
        int rightCol = grayMat.width() - 1;
        int bottomRow = grayMat.height() - 1;

        // 上方黑边判断
        for (int row = 0; row < grayMat.height(); row++) {
            // 判断当前行是否基本“全黑”，阈值自定义；
            if (sum(grayMat.row(row)) / grayMat.width() < blackValue) {
                // 更新截取条件
                topRow = row;
            } else {
                break;
            }
        }
        // 左边黑边判断
        for (int col = 0; col < grayMat.width(); col++) {
            // 判断当前列是否基本“全黑”，阈值自定义；
            if (sum(grayMat.col(col)) / grayMat.height() < blackValue) {
                // 更新截取条件
                leftCol = col;
            } else {
                break;
            }
        }
        // 右边黑边判断
        for (int col = grayMat.width() - 1; col > 0; col--) {
            // 判断当前列是否基本“全黑”，阈值自定义；
            if (sum(grayMat.col(col)) / grayMat.height() < blackValue) {
                // 更新截取条件
                rightCol = col;
            } else {
                break;
            }
        }
        // 下方黑边判断
        for (int row = grayMat.height() - 1; row > 0; row--) {
            // 判断当前行是否基本“全黑”，阈值自定义；
            if (sum(grayMat.row(row)) / grayMat.width() < blackValue) {
                // 更新截取条件
                bottomRow = row;
            } else {
                break;
            }
        }

        int x = leftCol;
        int y = topRow;
        int width = rightCol - leftCol;
        int height = bottomRow - topRow;

        if (leftCol == 0 && rightCol == grayMat.width() - 1 && topRow == 0 && bottomRow == grayMat.height() - 1) {
            return srcMat;
        }
        return cut(smallMat, x, y, width, height);
    }

    /**
     * 求和
     *
     * @param mat mat
     * @return sum
     */
    private static int sum(Mat mat) {
        int sum = 0;
        for (int row = 0; row < mat.height(); row++) {
            for (int col = 0; col < mat.width(); col++) {
                sum += mat.get(row, col)[0];
            }
        }
        return sum;
    }

测试代码：
类：ImageUtilsTest.java

    @Test
    public void testRemoveBlackEdge() {
        Mat mat = Imgcodecs.imread("/tmp/999.jpg");
        Mat result = ImageUtils.removeBlackEdge(mat);
        showImg(result);
    }

    @Test
    public void testRemoveBlackEdge2() {
        Mat mat = Imgcodecs.imread("/tmp/999.jpg");
        Mat result = ImageUtils.removeBlackEdge(mat, 5);
        showImg(result);
    }

结果：
原图：

testRemoveBlackEdge

testRemoveBlackEdge2

maven依赖，各区所需吧

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>cn.edu.zua.javacv</groupId>
    <artifactId>javacv</artifactId>
    <version>1.0-SNAPSHOT</version>

    <name>javacv</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>
    <description>测试javacv</description>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>

        <javacpp.platform.dependencies>windows-x86_64</javacpp.platform.dependencies>

        <!--util-->
        <util.mytool-core>1.0</util.mytool-core>

        <!--下面的平台只是用来参考配置 javacpp.platform.dependencies-->
        <javacpp.platform.android-arm>android-arm</javacpp.platform.android-arm>
        <javacpp.platform.android-arm64>android-arm64</javacpp.platform.android-arm64>
        <javacpp.platform.android-x86>android-x86</javacpp.platform.android-x86>
        <javacpp.platform.android-x86_64>android-x86_64</javacpp.platform.android-x86_64>
        <javacpp.platform.ios-arm>ios-arm</javacpp.platform.ios-arm>
        <javacpp.platform.ios-arm64>ios-arm64</javacpp.platform.ios-arm64>
        <javacpp.platform.ios-x86>ios-x86</javacpp.platform.ios-x86>
        <javacpp.platform.ios-x86_64>ios-x86_64</javacpp.platform.ios-x86_64>
        <javacpp.platform.linux-armhf>linux-armhf</javacpp.platform.linux-armhf>
        <javacpp.platform.linux-arm64>linux-arm64</javacpp.platform.linux-arm64>
        <javacpp.platform.linux-ppc64le>linux-ppc64le</javacpp.platform.linux-ppc64le>
        <javacpp.platform.linux-x86>linux-x86</javacpp.platform.linux-x86>
        <javacpp.platform.linux-x86_64>linux-x86_64</javacpp.platform.linux-x86_64>
        <javacpp.platform.macosx-x86_64>macosx-x86_64</javacpp.platform.macosx-x86_64>
        <javacpp.platform.windows-x86>windows-x86</javacpp.platform.windows-x86>
        <javacpp.platform.windows-x86_64>windows-x86_64</javacpp.platform.windows-x86_64>
    </properties>

    <dependencies>
        <dependency>
            <groupId>cn.edu.zua.mytool</groupId>
            <artifactId>mytool-core</artifactId>
            <version>${util.mytool-core}</version>
        </dependency>

        <dependency>
            <groupId>org.bytedeco</groupId>
            <artifactId>javacv-platform</artifactId>
            <version>1.4.3</version>
            <classifier>${javacpp.platform.dependencies}</classifier>
        </dependency>

        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>6.14.3</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>
        <testSourceDirectory>${project.basedir}/src/test/java</testSourceDirectory>
        <resources>
            <resource>
                <directory>${basedir}/src/main/resources</directory>
            </resource>
            <resource>
                <directory>${basedir}/src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.jpg</include>
                </includes>
            </resource>
        </resources>

        <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
            <plugins>
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.0.0</version>
                </plugin>
                <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.7.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.20.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>2.5.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>2.8.2</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

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参考文章：https://blog.csdn.net/u_ascend/article/details/85064795