Detailed introduction to the method sample code of generating thumbnails in java

This article mainly introduces the method of java generating thumbnail , combined with specific examples The form analyzes various common graphics processing techniques involved in the process of generating thumbnails in Java. Friends in need can refer to the following.

This article describes the method of generating thumbnails in Java and shares it with you for your reference. The details are as follows:

package com.util;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
/**
* 生成压缩图
*
*/
public class ImageScale {
private int width;
private int height;
private int scaleWidth;
double support = (double) 3.0;
double PI = (double) 3.14159265358978;
double[] contrib;
double[] normContrib;
double[] tmpContrib;
int startContrib, stopContrib;
int nDots;
int nHalfDots;
/**
* Start: Use Lanczos filter to replace the original algorithm for image
* scaling. Lanczos improves quality of the scaled image modify by :blade
*/
public BufferedImage imageZoomOut(BufferedImage srcBufferImage, int w, int h) {
width = srcBufferImage.getWidth();
height = srcBufferImage.getHeight();
scaleWidth = w;
if (DetermineResultSize(w, h) == 1) {
return srcBufferImage;
}
CalContrib();
BufferedImage pbOut = HorizontalFiltering(srcBufferImage, w);
BufferedImage pbFinalOut = VerticalFiltering(pbOut, h);
return pbFinalOut;
}
/**
* 决定图像尺寸
*/
private int DetermineResultSize(int w, int h) {
double scaleH, scaleV;
// update by libra
double wt = w > width ? width : w;
double ht = h > height ? height : h;
scaleH = (double) wt / (double) width;
scaleV = (double) ht / (double) height;
// 需要判断一下scaleH，scaleV，不做放大操作
if (scaleH >= 1.0 && scaleV >= 1.0) {
return 1;
}
return 0;
} // end of DetermineResultSize()
private double Lanczos(int i, int inWidth, int outWidth, double Support) {
double x;
x = (double) i * (double) outWidth / (double) inWidth;
return Math.sin(x * PI) / (x * PI) * Math.sin(x * PI / Support)
/ (x * PI / Support);
} // end of Lanczos()
//
// Assumption: same horizontal and vertical scaling factor
//
private void CalContrib() {
nHalfDots = (int) ((double) width * support / (double) scaleWidth);
nDots = nHalfDots * 2 + 1;
try {
contrib = new double[nDots];
normContrib = new double[nDots];
tmpContrib = new double[nDots];
} catch (Exception e) {
System.out.println("init contrib,normContrib,tmpContrib" + e);
}
int center = nHalfDots;
contrib[center] = 1.0;
double weight = 0.0;
int i = 0;
for (i = 1; i <= center; i++) {
contrib[center + i] = Lanczos(i, width, scaleWidth, support);
weight += contrib[center + i];
}
for (i = center - 1; i >= 0; i--) {
contrib[i] = contrib[center * 2 - i];
}
weight = weight * 2 + 1.0;
for (i = 0; i <= center; i++) {
normContrib[i] = contrib[i] / weight;
}
for (i = center + 1; i < nDots; i++) {
normContrib[i] = normContrib[center * 2 - i];
}
} // end of CalContrib()
// 处理边缘
private void CalTempContrib(int start, int stop) {
double weight = 0;
int i = 0;
for (i = start; i <= stop; i++) {
weight += contrib[i];
}
for (i = start; i <= stop; i++) {
tmpContrib[i] = contrib[i] / weight;
}
} // end of CalTempContrib()
private int GetRedValue(int rgbValue) {
int temp = rgbValue & 0x00ff0000;
return temp >> 16;
}
private int GetGreenValue(int rgbValue) {
int temp = rgbValue & 0x0000ff00;
return temp >> 8;
}
private int GetBlueValue(int rgbValue) {
return rgbValue & 0x000000ff;
}
private int ComRGB(int redValue, int greenValue, int blueValue) {
return (redValue << 16) + (greenValue << 8) + blueValue;
}
// 行水平滤波
private int HorizontalFilter(BufferedImage bufImg, int startX, int stopX,
int start, int stop, int y, double[] pContrib) {
double valueRed = 0.0;
double valueGreen = 0.0;
double valueBlue = 0.0;
int valueRGB = 0;
int i, j;
for (i = startX, j = start; i <= stopX; i++, j++) {
valueRGB = bufImg.getRGB(i, y);
valueRed += GetRedValue(valueRGB) * pContrib[j];
valueGreen += GetGreenValue(valueRGB) * pContrib[j];
valueBlue += GetBlueValue(valueRGB) * pContrib[j];
}
valueRGB = ComRGB(Clip((int) valueRed), Clip((int) valueGreen),
Clip((int) valueBlue));
return valueRGB;
} // end of HorizontalFilter()
// 图片水平滤波
private BufferedImage HorizontalFiltering(BufferedImage bufImage, int iOutW) {
int dwInW = bufImage.getWidth();
int dwInH = bufImage.getHeight();
int value = 0;
BufferedImage pbOut = new BufferedImage(iOutW, dwInH,
BufferedImage.TYPE_INT_RGB);
for (int x = 0; x < iOutW; x++) {
int startX;
int start;
int X = (int) (((double) x) * ((double) dwInW) / ((double) iOutW) + 0.5);
int y = 0;
startX = X - nHalfDots;
if (startX < 0) {
startX = 0;
start = nHalfDots - X;
} else {
start = 0;
}
int stop;
int stopX = X + nHalfDots;
if (stopX > (dwInW - 1)) {
stopX = dwInW - 1;
stop = nHalfDots + (dwInW - 1 - X);
} else {
stop = nHalfDots * 2;
}
if (start > 0 || stop < nDots - 1) {
CalTempContrib(start, stop);
for (y = 0; y < dwInH; y++) {
value = HorizontalFilter(bufImage, startX, stopX, start,
stop, y, tmpContrib);
pbOut.setRGB(x, y, value);
}
} else {
for (y = 0; y < dwInH; y++) {
value = HorizontalFilter(bufImage, startX, stopX, start,
stop, y, normContrib);
pbOut.setRGB(x, y, value);
}
}
}
return pbOut;
} // end of HorizontalFiltering()
private int VerticalFilter(BufferedImage pbInImage, int startY, int stopY,
int start, int stop, int x, double[] pContrib) {
double valueRed = 0.0;
double valueGreen = 0.0;
double valueBlue = 0.0;
int valueRGB = 0;
int i, j;
for (i = startY, j = start; i <= stopY; i++, j++) {
valueRGB = pbInImage.getRGB(x, i);
valueRed += GetRedValue(valueRGB) * pContrib[j];
valueGreen += GetGreenValue(valueRGB) * pContrib[j];
valueBlue += GetBlueValue(valueRGB) * pContrib[j];
// System.out.println(valueRed+"->"+Clip((int)valueRed)+"<-");
//
// System.out.println(valueGreen+"->"+Clip((int)valueGreen)+"<-");
// System.out.println(valueBlue+"->"+Clip((int)valueBlue)+"<-"+"-->");
}
valueRGB = ComRGB(Clip((int) valueRed), Clip((int) valueGreen),
Clip((int) valueBlue));
// System.out.println(valueRGB);
return valueRGB;
} // end of VerticalFilter()
private BufferedImage VerticalFiltering(BufferedImage pbImage, int iOutH) {
int iW = pbImage.getWidth();
int iH = pbImage.getHeight();
int value = 0;
BufferedImage pbOut = new BufferedImage(iW, iOutH,
BufferedImage.TYPE_INT_RGB);
for (int y = 0; y < iOutH; y++) {
int startY;
int start;
int Y = (int) (((double) y) * ((double) iH) / ((double) iOutH) + 0.5);
startY = Y - nHalfDots;
if (startY < 0) {
startY = 0;
start = nHalfDots - Y;
} else {
start = 0;
}
int stop;
int stopY = Y + nHalfDots;
if (stopY > (int) (iH - 1)) {
stopY = iH - 1;
stop = nHalfDots + (iH - 1 - Y);
} else {
stop = nHalfDots * 2;
}
if (start > 0 || stop < nDots - 1) {
CalTempContrib(start, stop);
for (int x = 0; x < iW; x++) {
value = VerticalFilter(pbImage, startY, stopY, start, stop,
x, tmpContrib);
pbOut.setRGB(x, y, value);
}
} else {
for (int x = 0; x < iW; x++) {
value = VerticalFilter(pbImage, startY, stopY, start, stop,
x, normContrib);
pbOut.setRGB(x, y, value);
}
}
}
return pbOut;
} // end of VerticalFiltering()
int Clip(int x) {
if (x < 0)
return 0;
if (x > 255)
return 255;
return x;
}
/**
* End: Use Lanczos filter to replace the original algorithm for image
* scaling. Lanczos improves quality of the scaled image modify by :blade
*/
public boolean scale(String source, String target, int width, int height) {
File f = new File(source);
try {
BufferedImage bi = ImageIO.read(f);
BufferedImage out = null;
ImageScale scal = new ImageScale();
int _width = bi.getWidth();// add
int _height = bi.getHeight();// add
int[] _arr = this.getImageWidthAndHeight(_width, _height, width,
height);// add
// out = scal.imageZoomOut(bi, width, height);
out = scal.imageZoomOut(bi, _arr[0], _arr[1]);
File t = new File(target);
ImageIO.write(out, "jpg", t);
return true;
} catch (IOException e) {
e.printStackTrace();
return false;
}
}
/**
* 得到放大或者缩小后的比例
*
* @param W
* 图片原宽
* @param H
* 原高
* @param tarW
* 转换后的宽
* @param zoom
* 放大还是缩小
* @return 返回宽和高的数组
*/
private static int[] getImageWidthAndHeight(int orgW, int orgH, int avW,
int avH) {
int width = 0;
int height = 0;
if (orgW > 0 && orgH > 0) {
if (orgW / orgH >= avW / avH) {
if (orgW > avW) {
width = avW;
height = (orgH * avW) / orgW;
} else {
width = orgW;
height = orgH;
}
System.out.println("++Widht:" + width + " Height" + height);
} else {
if (orgH > avH) {
height = avH;
width = (orgW * avH) / orgH;
} else {
width = orgW;
height = orgH;
}
System.out.println("++Widht:" + width + " Height" + height);
}
}
int[] arr = new int[2];
arr[0] = width;
arr[1] = height;
// long start = System.currentTimeMillis();
// int width = 0;
// int height = 0;
// if ((W / tarW) >= (H / tarH)) {// 宽的缩小比例大于高的
// width = tarW;
// height = H * tarW / W;
// System.out.println(width + " " + height);
// } else {
// height = tarH;
// width = W * tarH / H;
// System.out.println(width + " " + height);
// }
// int[] arr = new int[2];
// arr[0] = width;
// arr[1] = height;
// long end = System.currentTimeMillis();
// System.out.println("宽高处理：" + (end - start));
return arr;
}
public void picscale(String source, String target, int w, int h) {
File f = new File(source);
int width = 0;
int height = 0;
try {
BufferedImage bi = ImageIO.read(f);
int[] arr = getImageWidthAndHeight(bi.getWidth(), bi.getHeight(),
w, h);
width = arr[0];
height = arr[1];
BufferedImage out = null;
ImageScale scal = new ImageScale();
out = scal.imageZoomOut(bi, width, height);
File t = new File(target);
ImageIO.write(out, "jpg", t);
} catch (IOException e) {
e.printStackTrace();
}
}
/**
*
*调用scale(源文件路径，保存路径，最大宽，最大高)
*
*
*/
public static void main(String[] args) {
ImageScale is = new ImageScale();
long start = System.currentTimeMillis();
is.scale("D:/nie.jpg", "D:/t6.jpg", 250, 194);
long end = System.currentTimeMillis();
System.out.println("时间：" + (end - start));
}
}

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