Thumbnail generation fails for certain image types

[BaolCristian]

Description:
I have encountered an issue where the library fails to generate thumbnails for specific types of images. Below are the details:
• Problem: When trying to create thumbnails for certain image files, the process fails and no thumbnail is generated.
• Image Types Affected: PNG (in attach)
• Error Details: no errors, but the file is not saved
• Steps to Reproduce:

                InputStream is = new BufferedInputStream(img.getBinaryStream())
                def result=Thumbnails.of(is).size(width, height).asBufferedImage()
                ByteArrayOutputStream os = new ByteArrayOutputStream();
                ImageIO.write(result, "jpeg", os);
                // Passing: ​(RenderedImage im, String formatName, OutputStream output)
                InputStream fis = new ByteArrayInputStream(os.toByteArray());
                Connection conn = dataSource.getConnection()
                PreparedStatement pst
                if (isMax) pst = conn.prepareStatement("UPDATE FILES SET thumbnail_max = ? WHERE ID = ?")
                else pst = conn.prepareStatement("UPDATE FILES SET thumbnail = ? WHERE ID = ?")
                //= conn.prepareStatement("UPDATE FILES SET thumbnail = ? WHERE ID = ?")
                pst.setBinaryStream(1, fis, fis.available())
                pst.setLong(2, image.id)
                def index = pst.executeUpdate()
                pst.close()
                conn.close()

Environment:
• Library version: 0.4.20
• Operating System: MAC OS X /LINUX
• Programming Language and Version: GRAILS 4

[coobird]

@BaolCristian, I'm unable to reproduce the issue you're having with the image you've attached.

Here's the code I used to reproduce locally:

        InputStream is = new BufferedInputStream(new FileInputStream("404942059-a2d3755d-ddfa-48ef-9f24-2081ce12a550.png"));
        BufferedImage image = Thumbnails.of(is)
                .size(400, 400)
                .asBufferedImage();

Thumbnailator was able to create a BufferedImage without issue on a Ubuntu 24.04 box, running Java 8 using Thumbnailator 0.4.20.

Given that the provided code snippet contains a lot of other JDBC code, I'd recommend you double check those parts. Also, you may want to check if a minimal example like the one I posted above works or not. If it doesn't work, then it might be an environmental issue, so it'll be helpful if you can provide more details like OS version, framework version, and JRE version. Thanks!

[BaolCristian]

It turned out that ImageIO.write(...) was silently failing — most likely because the input image was in a format with an alpha channel (like TYPE_4BYTE_ABGR), which isn’t fully supported for JPEG output.

Working Solution:

To resolve the issue, I explicitly converted the resulting thumbnail to BufferedImage.TYPE_INT_RGB before passing it to ImageIO.write(...). This ensures that the image is compatible with the JPEG format, which does not support transparency.

BufferedImage thumb = Thumbnails.of(is).size(width, height).asBufferedImage()

BufferedImage rgbThumb = new BufferedImage(thumb.width, thumb.height, BufferedImage.TYPE_INT_RGB)
rgbThumb.graphics.drawImage(thumb, 0, 0, null)

boolean success = ImageIO.write(rgbThumb, "jpeg", os)