java:图像矩阵90,270度原地旋转的java实现

港控/mmm° 2022-03-11 16:12 219阅读 0赞

对图像矩阵原地旋转(In-place matrix transposition)的好处就是不用占用额外内存，所以在一些资源比较紧张的应用场景，原地旋转就显得必要了。  
参照这篇文章：[《opencv图像原地（不开辟新空间）顺时旋转90度》][opencv_90]，我实现了java代码，90,270度。  
原理就不详述了，上面这篇文章讲得已经很清楚，  
以下是实现代码：

/**
    	 * 图像顺时针旋转90度
    	 * @param input
    	 * @param width
    	 * @param height
    	 * @param bpp
    	 */
    	public static void rotate90(byte[] input,int width,int height,int bpp) {
        
    		if (input.length != width * height * bpp) {
        
    			throw new IllegalArgumentException("INVALID INPUT SIZE");
    		}
    		byte[] tmp = new byte[bpp];
    		for (int i = 0; i < width; i++) 
    		{
        
    			for (int j = 0; j < height; j++) 
    			{
        
    				int I = height - 1 - j;
    				int J = i;
    				while ((i*height + j) > (I*width + J))
    				{
        
    					int p = I*width + J;
    					int tmp_i = p / height;
    					int tmp_j = p % height;
    					I = height - 1 - tmp_j;
    					J = tmp_i;
    				} 
    				swap(input,(i*height + j)*bpp, (I*width + J)*bpp, bpp, tmp);
    			}
    		}
    	}
    	/**
    	 * 图像顺时针旋转270度
    	 * @param input
    	 * @param width
    	 * @param height
    	 * @param bpp
    	 */
    	public static void rotate270(byte[] input,int width,int height,int bpp) {
        
    		if (input.length != width * height * bpp) {
        
    			throw new IllegalArgumentException("INVALID INPUT SIZE");
    		}
    		byte[] tmp = new byte[bpp];
    		for (int i = 0; i < width; i++) 
    		{
        
    			for (int j = 0; j < height; j++) 
    			{
        
    				int I = j;
    				int J = width - 1 - i;
    				while ((i*height + j) > (I*width + J))
    				{
        
    					int p = I*width + J;
    					int tmp_i = p / height;
    					int tmp_j = p % height;
    					I = tmp_j;
    					J = width - 1 - tmp_i;
    				} 
    				swap(input,(i*height + j)*bpp, (I*width + J)*bpp, bpp, tmp);
    			}
    		}
    		
    	}
    	/**
    	 * 对数据array中x和y指向的数据交换
    	 * @param array 
    	 * @param x 
    	 * @param y
    	 * @param size 数据交换长度
    	 * @param tmp 用于数据交换的临时缓冲区，长度必须>= size
    	 */
    	private static void swap(byte[] array,int x,int y, int size, byte[] tmp){
        
    		System.arraycopy(array, x, tmp, 0, size);
    		System.arraycopy(array, y, array, x, size);
    		System.arraycopy(tmp, 0, array, y, size);
    	}

完整代码参见gitee仓库：[https://gitee.com/l0km/jimgutil/blob/master/jimgutil/src/main/java/gu/jimgutil/CsCvtUniImpl.java][https_gitee.com_l0km_jimgutil_blob_master_jimgutil_src_main_java_gu_jimgutil_CsCvtUniImpl.java]  
测试代码参见：[https://gitee.com/l0km/jimgutil/blob/master/jimgutil/src/test/java/gu/jimgutil/RotateTest.java][https_gitee.com_l0km_jimgutil_blob_master_jimgutil_src_test_java_gu_jimgutil_RotateTest.java]

# 参考资料 #

[《opencv图像原地（不开辟新空间）顺时旋转90度》][opencv_90]  
[《In-place\_matrix\_transposition》][In-place_matrix_transposition]

[opencv_90]: https://blog.csdn.net/seanwang_25/article/details/43273593?tdsourcetag=s_pcqq_aiomsg
[https_gitee.com_l0km_jimgutil_blob_master_jimgutil_src_main_java_gu_jimgutil_CsCvtUniImpl.java]: https://gitee.com/l0km/jimgutil/blob/master/jimgutil/src/main/java/gu/jimgutil/CsCvtUniImpl.java
[https_gitee.com_l0km_jimgutil_blob_master_jimgutil_src_test_java_gu_jimgutil_RotateTest.java]: https://gitee.com/l0km/jimgutil/blob/master/jimgutil/src/test/java/gu/jimgutil/RotateTest.java
[In-place_matrix_transposition]: https://en.wikipedia.org/wiki/In-place_matrix_transposition