How to read size and resize image without graphics (Thumbnail)

現今操作圖片都是使用java awt, awt裡提供getScaleInstance, 這個被批得半死, performance差的要死, 所以陸續其它人提出一些方式, 再測試過那些方式之後, 發現java 早在1.1的時代, 就有JIMI, 不知道是不是因為太舊了, 所以大家都把他遺忘了, 而改去用後來的ImageIO.

Java Image Management Interface, JIMI

要使用JIMI就如JMF一樣, 先到http://java.sun.com/products/jimi/

下載jar檔回來即可import.

/**

 * Insert the method's description here.

 * Creation date: (8/12/01 6:28:37 PM)

 */

void writeWithResizeMediaTracker()

{

try

{

Image inImage = new ImageIcon("input.jpg").getImage();

//

int maxDim = 120;

double scale = (double) maxDim / (double) inImage.getHeight(null);

if (inImage.getWidth(null) > inImage.getHeight(null))

{

scale = (double) maxDim / (double) inImage.getWidth(null);

}

// Determine size of new image.

//One of them

// should equal maxDim.

int scaledW = (int) (scale * inImage.getWidth(null));

int scaledH = (int) (scale * inImage.getHeight(null));

//

//

System.out.println(">> " 

+ inImage.getSource().getClass() 

+ " aspect ratio = " 

+ scaledW + " , " + scaledH);

Image img = inImage.getScaledInstance(scaledW , scaledH, Image.SCALE_SMOOTH);

File outputFile = new File("output.jpg");

outputFile.delete();

JimiRasterImage raster = Jimi.createRasterImage(img.getSource());

FileOutputStream fos = new FileOutputStream(outputFile);

Jimi.putImage("image/jpeg", raster, fos);

fos.flush();

fos.close();

}

catch (Throwable t)

{

t.printStackTrace();

}

}

Usage:

Input: input.jpg

Output: output.jpg

MaxDim: 最大長邊的pixel數

Thx for Kaan: http://home.tiscali.nl/~bmc88/java/sbook/ http://home.tiscali.nl/~bmc88/java/sbook/0132.html