OpenCV概述
OpenCV做爲功能強大的計算機視覺開源框架,包含了500多個算法實現,而且還在不斷增加,其最新版本已經更新到3.2。其SDK支持Android與Java平臺開發,對於常見的圖像處理需求幾乎都可以滿足,理應成爲廣大Java與Android程序員的首先的圖像處理框架。Java中使用OpenCV的配置及其簡單,可以毫不客氣的說幾乎是零配置都可以。
一:配置
配置引入OpenCV相關jar包,首先要下載OpenCV的自解壓版本,下載地址:
http://opencv.org/opencv-3-2.html
然後拉到網頁的最下方,下載Windows自解壓開發包
下載好了雙擊解壓縮之後找到build路徑,顯示如下:
雙擊打開Java文件夾,
裏面有一個jar直接導入到Eclipse中的新建項目中去, 然後把x64裏面的dll文件copy到Eclipse中使用的Java JDK bin和jre/bin目錄下面即可。環境就配置好啦,簡單吧!配置好的最終項目結構:
二:加載圖像與像素操作
讀入一張圖像 -, 一句話搞定
Mat src = Imgcodecs.imread(imageFilePath);
if(src.empty()) return;
將Mat對象轉換爲BufferedImage對象
public BufferedImage conver2Image(Mat mat) {
int width = mat.cols();
int height = mat.rows();
int dims = mat.channels();
int[] pixels = new int[width*height];
byte[] rgbdata = new byte[width*height*dims];
mat.get(0, 0, rgbdata);
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_ARGB);
int index = 0;
int r=0, g=0, b=0;
for(int row=0; row<height; row++) {
for(int col=0; col<width; col++) {
if(dims == 3) {
index = row*width*dims + col*dims;
b = rgbdata[index]&0xff;
g = rgbdata[index+1]&0xff;
r = rgbdata[index+2]&0xff;
pixels[row*width+col] = ((255&0xff)<<24) |
((r&0xff)<<16) | ((g&0xff)<<8) | b&0xff;
}
if(dims == 1) {
index = row*width + col;
b = rgbdata[index]&0xff;
pixels[row*width+col] = ((255&0xff)<<24) |
((b&0xff)<<16) | ((b&0xff)<<8) | b&0xff;
}
}
}
setRGB( image, 0, 0, width, height, pixels);
return image;
}
將BufferedImage對象轉換爲Mat對象
public Mat convert2Mat(BufferedImage image) {
int width = image.getWidth();
int height = image.getHeight();
Mat src = new Mat(new Size(width, height), CvType.CV_8UC3);
int[] pixels = new int[width*height];
byte[] rgbdata = new byte[width*height*3];
getRGB( image, 0, 0, width, height, pixels );
int index = 0, c=0;
int r=0, g=0, b=0;
for(int row=0; row<height; row++) {
for(int col=0; col<width; col++) {
index = row*width + col;
c = pixels[index];
r = (c&0xff0000)>>16;
g = (c&0xff00)>>8;
b = c&0xff;
index = row*width*3 + col*3;
rgbdata[index] = (byte)b;
rgbdata[index+1] = (byte)g;
rgbdata[index+2] = (byte)r;
}
}
src.put(0, 0, rgbdata);
return src;
}
特別要說明一下,BufferedImage與Mat的RGB通道順序是不一樣,正好相反,在Mat對象中三通道的順序爲BGR而在BufferedImage中爲RGB。
從Mat中讀取全部像素(其中image爲Mat類型數據)
int width = image.cols();
int height = image.rows();
int dims = image.channels();
byte[] data = new byte[width*height*dims];
image.get(0, 0, data);
遍歷像素操作與保存改變
int index = 0;
int r=0, g=0, b=0;
for(int row=0; row<height; row++) {
for(int col=0; col<width*dims; col+=dims) {
index = row*width*dims + col;
b = data[index]&0xff;
g = data[index+1]&0xff;
r = data[index+2]&0xff;
r = 255 - r;
g = 255 - g;
b = 255 - b;
data[index] = (byte)b;
data[index+1] = (byte)g;
data[index+2] = (byte)r;
}
}
image.put(0, 0, data);
保存Mat對象爲圖像文件 - 一句話可以搞定
Imgcodecs.imwrite(filePath, src);
OpenCV代碼運行與測試
調節明暗程度 - 亮度降低
調節明暗程度 - 亮度提升
高斯模糊
銳化
梯度
灰度化
上述效果完整Java代碼如下:
package com.gloomyfish.opencvdemo;
import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.core.Size;
import org.opencv.imgproc.Imgproc;
public class ImageFilters {
/** - 反色處理 - */
public Mat inverse(Mat image) {
int width = image.cols();
int height = image.rows();
int dims = image.channels();
byte[] data = new byte[width*height*dims];
image.get(0, 0, data);
int index = 0;
int r=0, g=0, b=0;
for(int row=0; row<height; row++) {
for(int col=0; col<width*dims; col+=dims) {
index = row*width*dims + col;
b = data[index]&0xff;
g = data[index+1]&0xff;
r = data[index+2]&0xff;
r = 255 - r;
g = 255 - g;
b = 255 - b;
data[index] = (byte)b;
data[index+1] = (byte)g;
data[index+2] = (byte)r;
}
}
image.put(0, 0, data);
return image;
}
public Mat brightness(Mat image) {
// 亮度提升
Mat dst = new Mat();
Mat black = Mat.zeros(image.size(), image.type());
Core.addWeighted(image, 1.2, black, 0.5, 0, dst);
return dst;
}
public Mat darkness(Mat image) {
// 亮度降低
Mat dst = new Mat();
Mat black = Mat.zeros(image.size(), image.type());
Core.addWeighted(image, 0.5, black, 0.5, 0, dst);
return dst;
}
public Mat gray(Mat image) {
// 灰度
Mat gray = new Mat();
Imgproc.cvtColor(image, gray, Imgproc.COLOR_BGR2GRAY);
return gray;
}
public Mat sharpen(Mat image) {
// 銳化
Mat dst = new Mat();
float[] sharper = new float[]{0, -1, 0, -1, 5, -1, 0, -1, 0};
Mat operator = new Mat(3, 3, CvType.CV_32FC1);
operator.put(0, 0, sharper);
Imgproc.filter2D(image, dst, -1, operator);
return dst;
}
public Mat blur(Mat image) {
// 高斯模糊
Mat dst = new Mat();
Imgproc.GaussianBlur(image, dst, new Size(15, 15), 0);
return dst;
}
public Mat gradient(Mat image) {
// 梯度
Mat grad_x = new Mat();
Mat grad_y = new Mat();
Mat abs_grad_x = new Mat();
Mat abs_grad_y = new Mat();
Imgproc.Sobel(image, grad_x, CvType.CV_32F, 1, 0);
Imgproc.Sobel(image, grad_y, CvType.CV_32F, 0, 1);
Core.convertScaleAbs(grad_x, abs_grad_x);
Core.convertScaleAbs(grad_y, abs_grad_y);
grad_x.release();
grad_y.release();
Mat gradxy = new Mat();
Core.addWeighted(abs_grad_x, 0.5, abs_grad_y, 0.5, 10, gradxy);
return gradxy;
}
}
可以說簡單到哭,此外OpenCV For Java支持各種的圖像處理包括形態學操作,二值圖像分析、圖像特徵檢測與識別、模板匹配、直方圖相關功能等等。常見的機器學習算法與圖像分析方法。可以說是功能最強大的圖像處理SDK與開發平臺之一,本人繼續發掘分享!
特別注意
在調用之前,一定要加上這句話
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
目的是加載OpenCV API相關的DLL支持,沒有它是不會正確運行的。以上代碼與功能實現是基於JDK8 64位與OpenCV 3.2版本。
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