Example of java's method for generating thumbnails

This article illustrates how java generates thumbnails. To share for your reference, specific as follows:

package com.util;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
/**
*  Generate compression diagram 
*
*/
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;
}
/**
*  Determine image size 
*/
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;
//  You need to determine 1 Under the scaleH . scaleV Do not zoom in 
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()
//  Deal with edge 
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;
}
//  Line horizontal filtering 
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()
//  Horizontal image filtering 
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;
}
}
/**
*  To get the scale of enlargement or reduction 
*
* @param W
*  Picture the original width 
* @param H
*  The original high 
* @param tarW
*  Converted width 
* @param zoom
*  Zoom in or out 
* @return  Returns an array of width and height 
*/
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)) {//  The width decreases in proportion to the height 
// 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(" Width and height treatment: " + (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();
}
}
/**
*
* call scale( Source file path, save path, maximum width, maximum height )
*
*
*/
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(" Time: " + (end - start));
}
}

PS: Here are some more practical photo processing tools for your reference:

BASE64 online Image conversion tool:
http://tools.ofstack.com/transcoding/img2base64

ICO Icon online generation tool:
http://tools.ofstack.com/aideddesign/ico_img

Online Email Email Icon Making Tool:
http://tools.ofstack.com/email/emaillogo

Online image format conversion (jpg/bmp/gif/png) tools:
http://tools.ofstack.com/aideddesign/picext

More java related content interested readers can view the site special topics: Java picture operation skills summary, java Date and time operation skills Summary, Java Operation DOM node skills Summary, Java File and directory operation skills Summary and Java Data Structure and Algorithm Tutorial.

I hope this article has been helpful in java programming.