java產生縮圖

因開發網站上大部份的圖均是透過管理介面讓管理者自行維運，
但有些圖檔過大，
故寫了一段產生縮圖的程式以免使用開啟網頁時塞爆頻寬。

1.指定圖檔寬度 : 傳入來源檔路徑(含檔名)、目的檔路徑(含檔名)、檔案副檔名、寬度

   public void change2SmallImg_w(String fromImgPath, String destImgPath, String imgType, int maxWidth) {
        try {
            File fiBig = new File(fromImgPath);
            File foSmall = new File(destImgPath);

            AffineTransform transform = new AffineTransform();
            BufferedImage bis = ImageIO.read(fiBig);
            //原来的高宽
            int w = bis.getWidth();
            int h = bis.getHeight();
            
            //等比例缩放　
            int nowWidth = maxWidth;
            int nowHeight = (nowWidth * h) / w;
            if (nowHeight > maxWidth) {
                nowHeight = maxWidth;
                nowWidth = (nowHeight * w) / h;
            }

            double sx = (double) nowWidth / w;
            double sy = (double) nowHeight / h;

            transform.setToScale(sx, sy);

            AffineTransformOp ato = new AffineTransformOp(transform, null);
            BufferedImage bid = new BufferedImage(nowWidth, nowHeight,
                    (imgType.compareToIgnoreCase("png") == 0) 
                        ? BufferedImage.TYPE_INT_ARGB : BufferedImage.TYPE_3BYTE_BGR);
            ato.filter(bis, bid);
            
            ImageIO.write(bid, imgType, foSmall);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

2.指定圖檔高度 : 傳入來源檔路徑(含檔名)、目的檔路徑(含檔名)、檔案副檔名、高度

   public void change2SmallImg_h(String fromImgPath, String destImgPath, String imgType, int maxHeight) {
        try {
            File fiBig = new File(fromImgPath);
            File foSmall = new File(destImgPath);

            AffineTransform transform = new AffineTransform();
            BufferedImage bis = ImageIO.read(fiBig);
            //原来的高宽
            int w = bis.getWidth();
            int h = bis.getHeight();
            
            //等比例缩放　
            int nowHeight = maxHeight;
            int nowWidth = (nowHeight * w) / h;
            if (nowWidth > maxHeight) {
                nowWidth = maxHeight;
                nowHeight = (nowWidth * h) / w;
            }

            double sx = (double) nowWidth / w;
            double sy = (double) nowHeight / h;

            transform.setToScale(sx, sy);

            AffineTransformOp ato = new AffineTransformOp(transform, null);
            BufferedImage bid = new BufferedImage(nowWidth, nowHeight,
                    (imgType.compareToIgnoreCase("png") == 0) 
                        ? BufferedImage.TYPE_INT_ARGB : BufferedImage.TYPE_3BYTE_BGR);
            ato.filter(bis, bid);
            
            ImageIO.write(bid, imgType, foSmall);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }