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POResizing BufferedImages and storing them to file results in black background for JPG images
 

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  1. POResizing BufferedImages and storing them to file results in black background for JPG images
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    <p>I have the following code:</p> <pre><code>import java.awt.Graphics2D; import java.awt.Image; import java.awt.image.BufferedImage; import java.io.File; import javax.imageio.ImageIO; public class JavaApplication { public static void main(String[] args) throws Exception { File orig = new File ("/home/xxx/Pictures/xxx.jpg"); BufferedImage bm1 = ImageIO.read(orig); Image scaled = bm1.getScaledInstance(100, 200, BufferedImage.SCALE_SMOOTH); BufferedImage bm2 = toBufferedImage(scaled); File resized = new File ("/home/xxx/Pictures/resized.jpg"); ImageIO.write(bm2, "jpg", resized); } public static BufferedImage toBufferedImage(Image img) { if (img instanceof BufferedImage) { return (BufferedImage) img; } BufferedImage bimage = new BufferedImage(img.getWidth(null), img.getHeight(null), BufferedImage.TYPE_INT_ARGB); bimage.getGraphics().drawImage(img, 0, 0 , null); return bimage; } } </code></pre> <p>If I use this code on a .png file, it works fine, and resizes the file as expected. However on jpg files, it results in a black background.</p> <p>If I remove the <code>getScaledInstance()</code> code and simply try to re-write the original <code>bm1</code> to the disk using <code>ImageIO.write(bm1, "jpg", resized)</code>, that works fine. Only when resizing using <code>getScaledInstance()</code> and then trying to conver the resulting <code>Image</code> back to <code>BufferedImage</code>, do I get a completely black background file.</p> <p>Any ideas on how to fix this, or what I'm doing wrong?</p>
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    1. COIt's been too long since I've done image scaling, but I always found this article useful: https://today.java.net/pub/a/today/2007/04/03/perils-of-image-getscaledinstance.html. Maybe some of the techniques in there will help?
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    2. CO@Ash Can you give me a tl;dr of this? I'm not using `Image.getScaledInstance()` anyway, I'm using `BufferedImage.getScaledInstance()`.
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    3. COYour problem is that you are using `getScaledInstance()`. It returns immediately with an `Image`, *but the image is not yet scaled at this point*. So when you later invoke `drawImage` using this image, it's effectively a no-op. Update: There's no difference if you inkoke `getScaledInstance` on an `Image` or a `BufferedImage`.
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