在app的后台中，有时候为了标示版权，需要给图片加上水印。

在liunx中，IM4JAVA+GraphicsMagick是个高效处理图片的方案，图片的裁剪是使用了这个技术方案，为了减少不必要的开发成本和运维成本，对应水印，我们是打算继续采用这个方案。

但在开发的过程中，发现这个方案对中文水印支持得不好。

根据网上的搜索结果，就算采用了im4java的GMOperation，并将水印的字符串转成GBK的编码，添加中文水印时，对于奇数个数的中文，没问题；但对于偶数个数的中文，就出现乱码了。

试了多次后，发现这个问题没法解决，于是试了JMagick+ ImageMagick。

但是，在网上找到一份资料，http://javantsky.iteye.com/blog/747807， 里面提到JMagick+ImageMagick作为应用服务的缺点，并建议可以使用IM4JAVA：

The "JNI hazard" here is that if something you use (f.ex libtiff for reading

TIFF files) has a memory bug then it can make your whole JVM crash. Thats of

course frustrating and therefore its great to have im4java around, which

starts IM as an external process, so JVM crashes are avoided.

* *

Coolest thing would be if JMagick and im4java could have the same API so it

was easy to switch depending on luckyness. Ive asked the author of im4java

to attemt to be as compatible as possible, but as im4java is very much

different internally its limited how much can be done in that direction.

If you don't like the risk, stick to im4java. If your want optimal

performance give JMagick a try.

And, its not JMagick that is buggy, its what it depends on (hereunder IM)

that is not always (memory) bug free on long running processes.

I also have never seen a mismatch between JMagick binary and ImageMagick

binaries leading to crashes.

最后，采用了以下的方案视线图片的中文水印：

1.先把中文生成背景透明的png图片

2.把这些png图片作为图片水印贴在图上

代码如下：

package test;

import java.awt.BasicStroke;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.Image;

import java.awt.Transparency;

import java.awt.font.FontRenderContext;

import java.awt.geom.AffineTransform;

import java.awt.geom.Rectangle2D;

import java.awt.image.BufferedImage;

import java.io.File;

import java.io.IOException;

import javax.imageio.ImageIO;

import org.im4java.core.CompositeCmd;

import org.im4java.core.ConvertCmd;

import org.im4java.core.GMOperation;

import org.im4java.core.GraphicsMagickCmd;

import org.im4java.core.IM4JavaException;

import org.im4java.core.IMOperation;

public class Watermark {

/**

* 按九宫格位置添加水印

* @param srcPath原图片路径

* @param distPath新图片路径

* @param watermarkImg水印图片路径

* @param position九宫格位置[1-9],从上往下,从左到右排序

* @param x 横向边距

* @param y 纵向边距

* @param alpha透明度

* @throws IOException

* @throws InterruptedException

* @throws IM4JavaException

*/

public void WatermarkImg(String srcPath,String distPath,String watermarkImg, int position, int x, int y, int alpha) throws IOException, InterruptedException, IM4JavaException{

int[] watermarkImgSide = getImageSide(watermarkImg);

int[] srcImgSide = getImageSide(srcPath);

int[] xy = getXY(srcImgSide, watermarkImgSide, position, y, x);

watermarkImg(srcPath,distPath,watermarkImg,watermarkImgSide[0],watermarkImgSide[1],xy[0],xy[1],alpha);

}

private int[] getImageSide(String imgPath) throws IOException {

int[] side = new int[2];

Image img = ImageIO.read(new File(imgPath));

side[0] = img.getWidth(null);

side[1] =img.getHeight(null);

return side;

}

/**

* 添加图片水印

* @param srcPath原图片路径

* @param distPath新图片路径

* @param watermarkImg水印图片路径

* @param width水印宽度(可以于水印图片大小不同)

* @param height水印高度(可以于水印图片大小不同)

* @param x水印开始X坐标

* @param y水印开始Y坐标

* @param alpha透明度[0-100]

* @throws IOException

* @throws InterruptedException

* @throws IM4JavaException

*/

private synchronized void watermarkImg(String srcPath,String distPath,String watermarkImg, int width, int height, int x, int y, int alpha) throws IOException, InterruptedException, IM4JavaException{

CompositeCmd cmd = new CompositeCmd(true);

String path = "C://Program Files//GraphicsMagick-1.3.19-Q8";

cmd.setSearchPath(path);

IMOperation op = new IMOperation();

op.dissolve(alpha);

op.geometry(width, height, x, y);

op.addImage(watermarkImg);

op.addImage(srcPath);

op.addImage(distPath);

cmd.run(op);

}

private int[] getXY(int[] image, int[] watermark, int position, int x, int y) {

int[] xy = new int[2];

if(position==1){

xy[0] = x;

xy[1] = y;

}else if(position==2){

xy[0] = (image[0]-watermark[0])/2;//横向边距

xy[1] = y; //纵向边距

}else if(position==3){

xy[0] = image[0]-watermark[0]-x;

xy[1] = y;

}else if(position==4){

xy[0] = x;

xy[1] = (image[1]-watermark[1])/2;

}else if(position==5){

xy[0] = (image[0]-watermark[0])/2;

xy[1] = (image[1]-watermark[1])/2;

}else if(position==6){

xy[0] = image[0]-watermark[0]-x;

xy[1] = (image[1] - watermark[1])/2;

}else if(position==7){

xy[0] = x;

xy[1] = image[1] - watermark[1] - y;

}else if(position==8){

xy[0] = (image[0]-watermark[0])/2;

xy[1] = image[1] - watermark[1] - y;

}else{

xy[0] = image[0]-watermark[0]-x;

xy[1] = image[1] - watermark[1] - y;

}

return xy;

}

/**

* 把文字转化为一张背景透明的png图片

* @param str 文字的内容

* @param fontType 字体，例如宋体

* @param fontSize 字体大小

* @param colorStr 字体颜色，不带#号，例如"990033"

* @param outfile png图片的路径

* @throws Exception

*/

public void converFontToImage(String str,String fontType,int fontSize,String colorStr, String outfile) throws Exception{

Font font=new Font(fontType,Font.BOLD,fontSize);

File file=new File(outfile);

//获取font的样式应用在str上的整个矩形

Rectangle2D r=font.getStringBounds(str, new FontRenderContext(AffineTransform.getScaleInstance(1, 1),false,false));

int unitHeight=(int)Math.floor(r.getHeight());//获取单个字符的高度

//获取整个str用了font样式的宽度这里用四舍五入后+1保证宽度绝对能容纳这个字符串作为图片的宽度

int width=(int)Math.round(r.getWidth())+1;

int height=unitHeight+3;//把单个字符的高度+3保证高度绝对能容纳字符串作为图片的高度

//创建图片

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics2D g2d = image.createGraphics();

image = g2d.getDeviceConfiguration().createCompatibleImage(width, height, Transparency.TRANSLUCENT);

g2d.dispose();

g2d = image.createGraphics();

g2d.setColor(Color.WHITE);

g2d.setStroke(new BasicStroke(1));

g2d.setColor(new Color(Integer.parseInt(colorStr, 16)));//在换成所需要的字体颜色

g2d.setFont(font);

g2d.drawString(str, 0,font.getSize());

ImageIO.write(image, "png", file);//输出png图片

}

}

测试实例：

package test;

import java.awt.BasicStroke;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.Transparency;

import java.awt.font.FontRenderContext;

import java.awt.geom.AffineTransform;

import java.awt.geom.Rectangle2D;

import java.awt.image.BufferedImage;

import java.io.File;

import javax.imageio.ImageIO;

import org.im4java.core.CompositeCmd;

import org.im4java.core.ConvertCmd;

import org.im4java.core.GMOperation;

import org.im4java.core.IMOperation;

public class test {

public static void main(String[] args) {

try {

String src="D://src.jpg"; //需要加水印的源图片

String desc="D://desc.jpg"; //生成的水印图片的路径

String water="D://water.png"; //用中文转换成的背景透明的png图片

String fontType="C:\\Windows\\Fonts\\simsun.ttc"; //指定字体文件为宋体

String colorStr="990033"; //颜色

int fontSize=18;

Watermark watermark=new Watermark();

/*

* 把文字转化为一张背景透明的png图片

* @param str 文字的内容

* @param fontType 字体，例如宋体

* @param fontSize 字体大小

* @param colorStr 字体颜色，不带#号，例如"990033"

* @param outfile png图片的路径

* @throws Exception

*/

watermark.converFontToImage("中华人们", fontType, fontSize, colorStr, water);

/*

* 把文字的png图片贴在原图上，生成水印

* @param srcPath原图片路径

* @param distPath新图片路径

* @param watermarkImg水印图片路径

* @param position九宫格位置[1-9],从上往下,从左到右排序

* @param x 横向边距

* @param y 纵向边距

* @param alpha透明度

*/

watermark.WatermarkImg(src, desc, water, 1, 20,20, 100);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

源码已放在github：https://github.com/newjueqi/ChineseWaterMark#

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