JAVA 图像渐变暗化 graphics fillRect
前后折腾了大约有将近一天的工夫，终于完成了图像整体暗化（分分钟）和图像渐变暗化（近一天）的功能，时候才发现其实不应该急着写代码，仔仔细细地读文档是非常有必要的，可以少走很多的弯路。
大部分时间的浪费都是因为对Graphics中的方法的fillRect参数理解错误，在java文档中，是这样写的
public abstract void fillRect(int x,
int y,
int width,
int height)
于是我以为height就是要填充长方形区域的右下角的顶点位置，于是出来的图整个下半部分都是几乎全黑。后来自己用imageHelper.darkerImageBy()才发现原来用错了，在仔细读官方文档，看到是这样解释参数的：
Parameters:
x- the x coordinate of the rectangle to be drawn.
y- the y coordinate of the rectangle to be drawn.
width- the width of the rectangle to be drawn.
height- the height of the rectangle to be drawn.
也就是height并不是右下角点的纵坐标，而是长方形的高度，囧，改了之后瞬间出来了效果。
整体的处理是参考了stackoverflow上的这个回答。
下面是全部的实现代码
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
/**
* User: shellbye.com@gmail.com
*/
public class ImageHelper {
BufferedImage img;
Graphics graphics;
String orginalFileName;
String orginalFileExt;
String fileSaveToTemp;
float percentage = 0.5f;
public ImageHelper() {
}
public ImageHelper(File inputImage) throws IOException {
init(inputImage);
}
public void init(File image) throws IOException {
img = ImageIO.read(image);
orginalFileName = image.getName();
String[] temp = orginalFileName.split("\\.");
orginalFileExt = temp[temp.length - 1];
graphics = img.createGraphics();
}
public void getImage(String imageDir) throws IOException {
File inputImage = new File(imageDir);
init(inputImage);
}
public void darkerImageBy(float percentage) throws IOException {
percentage = 1 - percentage;
int brightness = (int) (256 - 256 * percentage);
graphics.setColor(new Color(0, 0, 0, brightness));
graphics.fillRect(0, 0, img.getWidth(), img.getHeight());
}
public void darkerImage2By(float percentage) throws IOException {
percentage = 1 - percentage;
int brightness = (int) (256 - 256 * percentage);
// 图像切割粒度，每fineness行划分为一个小块
int fineness = 2;
int degree = img.getHeight() / fineness;
int lastHeight = 0;
for (int i = 0; i < degree; i++) {
int tempBrightness = brightness * i / degree;
int tempHeight = img.getHeight() * i / degree;
graphics.setColor(new Color(0, 0, 0, tempBrightness));
graphics.fillRect(0, lastHeight, img.getWidth(), img.getHeight() / degree);
lastHeight = tempHeight + 1;
}
}
public void saveImageTo(String saveToDir) throws IOException {
File file = new File(saveToDir + System.currentTimeMillis() + "." + orginalFileExt);
ImageIO.write(img, orginalFileExt, file);
}
public static void main(String[] args) throws IOException {
ImageHelper imageHelper = new ImageHelper();
imageHelper.getImage("C://Users/Administrator/Desktop/1.png");
// imageHelper.darkerImageBy(0.50f);
imageHelper.darkerImage2By(0.80f);
imageHelper.saveImageTo("C://Users/Administrator/Desktop/");
}
}blog comments powered by Disqus