java生成缩略图的方法示例

java生成缩略图的方法示例

本文实例讲述了java生成缩略图的方法。分享给大家供大家参考，具体如下：

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 = srcBufferImXqWrFrQage.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;

startXqWrFrQ = 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 = aXqWrFrQvH;

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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