1. java上傳圖片 生成縮略圖，如果上傳的圖片尺寸比較小就壓縮處理
//將圖按比例縮小。
public static BufferedImage resize(BufferedImage source, int targetW, int targetH) {
// targetW，targetH分別表示目標長和寬
int type = source.getType();
BufferedImage target = null;
double sx = (double) targetW / source.getWidth();
double sy = (double) targetH / source.getHeight();
//這里想實現在targetW，targetH范圍內實現等比縮放。如果不需要等比縮放
//則將下面的if else語句注釋即可
if(sx>sy)
{
sx = sy;
targetW = (int)(sx * source.getWidth());
}else{
sy = sx;
targetH = (int)(sy * source.getHeight());
}
if (type == BufferedImage.TYPE_CUSTOM) { //handmade
ColorModel cm = source.getColorModel();
WritableRaster raster = cm.(targetW, targetH);
boolean alphaPremultiplied = cm.isAlphaPremultiplied();
target = new BufferedImage(cm, raster, alphaPremultiplied, null);
} else
target = new BufferedImage(targetW, targetH, type);
Graphics2D g = target.createGraphics();
//smoother than exlax:
g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY );
g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
g.dispose();
return target;
}
public static void saveImageAsJpg (String fromFileStr,String saveToFileStr,int width,int hight)
throws Exception {
BufferedImage srcImage;
// String ex = fromFileStr.substring(fromFileStr.indexOf("."),fromFileStr.length());
String imgType = "JPEG";
if (fromFileStr.toLowerCase().endsWith(".png")) {
imgType = "PNG";
}
// System.out.println(ex);
File saveFile=new File(saveToFileStr);
File fromFile=new File(fromFileStr);
srcImage = ImageIO.read(fromFile);
if(width > 0 || hight > 0)
{
srcImage = resize(srcImage, width, hight);
}
ImageIO.write(srcImage, imgType, saveFile);
}
public static void main (String argv[]) {
try{
//參數1(from),參數2(to),參數3(寬),參數4(高)
saveImageAsJpg("C:\\Documents and Settings\\xugang\\桌面\\tmr-06.jpg",
"C:\\Documents and Settings\\xugang\\桌面\\2.jpg",
120,120);
} catch(Exception e){
e.printStackTrace();
}
}
2. java類 圖片導入到excel 模糊 就是圖片被蓋上了一層紅色
Java上傳圖片時，對某些圖片進行縮放、裁剪或者生成縮略圖時會蒙上一層紅色，經過檢查只要經過ImageIO.read()方法讀取後再保存，該圖片便已經變成紅圖。因此，可以推測直接原因在於ImageIO.read()方法載入圖片的過程存在問題。
public static BufferedImage getImages(byte[] data) throws IOException {
ByteArrayInputStream input = new ByteArrayInputStream(data);
return ImageIO.read(input);
}
經過查閱得知ImageIO.read()方法讀取圖片時可能存在不正確處理圖片ICC信息的問題，ICC為JPEG圖片格式中的一種頭部信息，導致渲染圖片前景色時蒙上一層紅色。解決方案：
不再使用ImageIO.read()方法載入圖片，而使用JDK中提供的Image src=Toolkit.getDefaultToolkit().getImage
Image src=Toolkit.getDefaultToolkit().getImage(file.getPath());
BufferedImage image=BufferedImageBuilder.toBufferedImage(src);//Image to BufferedImage
或者Toolkit.getDefaultToolkit().createImage
Image imageTookit = Toolkit.getDefaultToolkit().createImage(bytes);
BufferedImage cutImage = BufferedImageBuilder.toBufferedImage(imageTookit);
BufferedImageBuilder源碼：
public static BufferedImage toBufferedImage(Image image) {
if (image instanceof BufferedImage) {
return (BufferedImage) image;
}
// This code ensures that all the pixels in the image are loaded
image = new ImageIcon(image).getImage();
BufferedImage bimage = null;
GraphicsEnvironment ge = GraphicsEnvironment
.getLocalGraphicsEnvironment();
try {
int transparency = Transparency.OPAQUE;
GraphicsDevice gs = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gs.getDefaultConfiguration();
bimage = gc.createCompatibleImage(image.getWidth(null),
image.getHeight(null), transparency);
} catch (HeadlessException e) {
// The system does not have a screen
}
if (bimage == null) {
// Create a buffered image using the default color model
int type = BufferedImage.TYPE_INT_RGB;
bimage = new BufferedImage(image.getWidth(null),
image.getHeight(null), type);
}
// Copy image to buffered image
Graphics g = bimage.createGraphics();
// Paint the image onto the buffered image
g.drawImage(image, 0, 0, null);
g.dispose();
return bimage;
}