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copied!<p>You don't need a full blown Image processing library for simply resizing an image.</p> <p>The recommended approach is by using <strong>progressive bilinear scaling</strong>, like so (feel free to use this method as is in your code):</p> <pre><code>public BufferedImage scale(BufferedImage img, int targetWidth, int targetHeight) { int type = (img.getTransparency() == Transparency.OPAQUE) ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB; BufferedImage ret = img; BufferedImage scratchImage = null; Graphics2D g2 = null; int w = img.getWidth(); int h = img.getHeight(); int prevW = w; int prevH = h; do { if (w > targetWidth) { w /= 2; w = (w < targetWidth) ? targetWidth : w; } if (h > targetHeight) { h /= 2; h = (h < targetHeight) ? targetHeight : h; } if (scratchImage == null) { scratchImage = new BufferedImage(w, h, type); g2 = scratchImage.createGraphics(); } g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR); g2.drawImage(ret, 0, 0, w, h, 0, 0, prevW, prevH, null); prevW = w; prevH = h; ret = scratchImage; } while (w != targetWidth || h != targetHeight); if (g2 != null) { g2.dispose(); } if (targetWidth != ret.getWidth() || targetHeight != ret.getHeight()) { scratchImage = new BufferedImage(targetWidth, targetHeight, type); g2 = scratchImage.createGraphics(); g2.drawImage(ret, 0, 0, null); g2.dispose(); ret = scratchImage; } return ret; } </code></pre> <p>Code modified and cleaned from the original at <a href="http://filthyrichclients.org" rel="noreferrer">Filthy Rich Clients</a>.</p> <hr> <p>Based on your comment, you can reduce quality and encode JPEG bytes like so:</p> <p><code>image</code> is the BufferedImage. </p> <pre><code>ByteArrayOutputStream os = new ByteArrayOutputStream(); ImageWriter writer = (ImageWriter) ImageIO.getImageWritersByFormatName("jpeg").next(); ImageWriteParam param = writer.getDefaultWriteParam(); param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); param.setCompressionQuality(0.2f); // Change this, float between 0.0 and 1.0 writer.setOutput(ImageIO.createImageOutputStream(os)); writer.write(null, new IIOImage(image, null, null), param); writer.dispose(); </code></pre> <p>Now, since <code>os</code> is a <code>ByteArrayOutputStream</code>, you can Base64 encode it.</p> <pre><code>String base64 = Base64.encode(os.toByteArray()); </code></pre>

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