Read PNG/JPEG/BMP/GIF dimensions without loading image data

[Riven]

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public static Dimension getImageDimension(File file) throws IOException    {       RandomAccessFile raf = new RandomAccessFile(file, "r");             try       {          int header = raf.readUnsignedShort();          if (header == 0x8950)          {             // PNG!             raf.seek(8 + 4 + 4); // thanks, Abuse             return new Dimension(raf.readInt(), raf.readInt());          }          if (header == 0xffd8)          {             // JPG!             // (see below)          }          else if (header == 0x424D)          {             // BMP!             raf.seek(0x0012);             int w = raf.read() | (raf.read() << 8) | (raf.read() << 16) | (raf.read() << 24);             int h = raf.read() | (raf.read() << 8) | (raf.read() << 16) | (raf.read() << 24);             return new Dimension(w, h);          }          else if (header == (('G' << 8) | ('I' << 0)))          {             // GIF!             raf.seek(0x0006);             int w = raf.read() | (raf.read() << 8);             int h = raf.read() | (raf.read() << 8);             return new Dimension(w, h);          }          else          {             throw new IllegalStateException("unexpected header: " + Integer.toHexString(header));          }          while (true) // JPG is not so easy...          {             int marker = raf.readUnsignedShort();             switch (marker)             {                case 0xffd8: // SOI                case 0xffd0: // RST0                case 0xffd1: // RST1                case 0xffd2: // RST2                case 0xffd3: // RST3                case 0xffd4: // RST4                case 0xffd5: // RST5                case 0xffd6: // RST6                case 0xffd7: // RST7                case 0xffd9: // EOI                   break;                case 0xffdd: // DRI                   raf.readUnsignedShort();                   break;                case 0xffe0: // APP0                case 0xffe1: // APP1                case 0xffe2: // APP2                case 0xffe3: // APP3                case 0xffe4: // APP4                case 0xffe5: // APP5                case 0xffe6: // APP6                case 0xffe7: // APP7                case 0xffe8: // APP8                case 0xffe9: // APP9                case 0xffea: // APPa                case 0xffeb: // APPb                case 0xffec: // APPc                case 0xffed: // APPd                case 0xffee: // APPe                case 0xffef: // APPf                case 0xfffe: // COM                case 0xffdb: // DQT                case 0xffc4: // DHT                case 0xffda: // SOS                   raf.readFully(new byte[raf.readUnsignedShort() - 2]);                   break;                case 0xffc0: // SOF0                case 0xffc2: // SOF2                   raf.readUnsignedShort();                   raf.readByte();                   int height = raf.readUnsignedShort();                   int width = raf.readUnsignedShort();                   return new Dimension(width, height);                default:                   throw new IllegalStateException("invalid jpg marker: " + Integer.toHexString(marker));             }          }       }       finally       {          raf.close();       }    } }

[Riven]

This version works on InputStreams too, which is required for loading your images through a classloader.

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public static Dimension getImageDimension(File file) throws IOException    {       return ImageUtil.getImageDimension(new FileInputStream(file));    }    public static Dimension getImageDimension(InputStream in) throws IOException    {       DataInputStream dis = new DataInputStream(in);       try       {          int header = dis.readUnsignedShort();          if (header == 0x8950)          {             // PNG!             dis.readFully(new byte[(8 - 2) + 4 + 4]); // thanks Abuse             return new Dimension(dis.readInt(), dis.readInt());          }          if (header == 0xffd8)          {             // JPG!             // (see below)          }          else if (header == 0x424D)          {             // BMP!             dis.readFully(new byte[16]);             int w = dis.read() | (dis.read() << 8) | (dis.read() << 16) | (dis.read() << 24);             int h = dis.read() | (dis.read() << 8) | (dis.read() << 16) | (dis.read() << 24);             return new Dimension(w, h);          }          else if (header == (('G' << 8) | ('I' << 0))) // GIF          {             // GIF!             dis.readFully(new byte[4]);             int w = dis.read() | (dis.read() << 8);             int h = dis.read() | (dis.read() << 8);             return new Dimension(w, h);          }          else          {             throw new IllegalStateException("unexpected header: " + Integer.toHexString(header));          }          while (true)          {             int marker = dis.readUnsignedShort();             switch (marker)             {                case 0xffd8: // SOI                case 0xffd0: // RST0                case 0xffd1: // RST1                case 0xffd2: // RST2                case 0xffd3: // RST3                case 0xffd4: // RST4                case 0xffd5: // RST5                case 0xffd6: // RST6                case 0xffd7: // RST7                case 0xffd9: // EOI                   break;                case 0xffdd: // DRI                   dis.readUnsignedShort();                   break;                case 0xffe0: // APP0                case 0xffe1: // APP1                case 0xffe2: // APP2                case 0xffe3: // APP3                case 0xffe4: // APP4                case 0xffe5: // APP5                case 0xffe6: // APP6                case 0xffe7: // APP7                case 0xffe8: // APP8                case 0xffe9: // APP9                case 0xffea: // APPa                case 0xffeb: // APPb                case 0xffec: // APPc                case 0xffed: // APPd                case 0xffee: // APPe                case 0xffef: // APPf                case 0xfffe: // COM                case 0xffdb: // DQT                case 0xffc4: // DHT                case 0xffda: // SOS                   dis.readFully(new byte[dis.readUnsignedShort() - 2]);                   break;                case 0xffc0: // SOF0                case 0xffc2: // SOF2                   dis.readUnsignedShort();                   dis.readByte();                   int height = dis.readUnsignedShort();                   int width = dis.readUnsignedShort();                   return new Dimension(width, height);                default:                   throw new IllegalStateException("invalid jpg marker: " + Integer.toHexString(marker));             }          }       }       finally       {          dis.close();       }    }

[Abuse]

Wouldn't it be nice if DataInput defined methods for reading primitives in LSB order as well as Java's chosen convention of MSB.

It seems such a simple yet incredibly useful thing to have missed off; and given the choice of zip for code package distribution it must have been an I/O necessity from the very beginning! (DEFLATE stores block lengths in LSB order)

Games published by our own members! Check 'em out!

[Riven]

Yup. Judging by how the naming convetions at Sun are (LayoutManager => LayoutManager2, NIO => NIO2) we could expect DataInput2 any day now.

[CaptainJester]

Wouldn't it be nice if DataInput defined methods for reading primitives in LSB order as well as Java's chosen convention of MSB.

It seems such a simple yet incredibly useful thing to have missed off; and given the choice of zip for code package distribution it must have been an I/O necessity from the very beginning! (DEFLATE stores block lengths in LSB order)

You could use a FileChannel.  Then when you create your ByteBuffer for reading from the channel you set the order to ByteOrder.LITTLE_ENDIAN or ByteOrder.BIG_ENDIAN.  Then from the ByteBuffer getFloat,getInt,getLong etc...

[Riven]

Yeah... but I'm working with InputStreams...

[CommanderKeith]

This is very useful, thanks.  May I ask, what are you using it for?

[Riven]

I have this webservice, that must scale huge images (8K * 4K pixels) to thumbnails. I use this code to determine whether the webservice (which has a small heap to keep FullGC down to a minimum) can handle it, or it should launch a new JVM to do it -- which might run out of memory, without taking down the webservice.

[Abuse]

I have this webservice, that must scale huge images (8K * 4K pixels) to thumbnails. I use this code to determine whether the webservice (which has a small heap to keep FullGC down to a minimum) can handle it, or it should launch a new JVM to do it -- which might run out of memory, without taking down the webservice.

Sounds like what you really want is a progressive decoder for all of said image formats 

[Riven]

Indeed. Me lazy.

BMP and PNG (RGB24/ARGB32) are trivial. JPG not so simple. JAI did not do it (dispite the promise), and I didn't want to spend more time on it, so this was a quick hack, that will probably be used for a few years.

Games published by our own members! Check 'em out!

[CaptainJester]

Yeah... but I'm working with InputStreams...

Feed the bytes into a ByteBuffer yourself.  Then you can still take advantage of the ByteOrder of a ByteBuffer.

[CommanderKeith]

I have this webservice, that must scale huge images (8K * 4K pixels) to thumbnails. I use this code to determine whether the webservice (which has a small heap to keep FullGC down to a minimum) can handle it, or it should launch a new JVM to do it -- which might run out of memory, without taking down the webservice.

Interesting. Clever solution. How annoying that JAI api can't do it.

[Riven]

Feed the bytes into a ByteBuffer yourself.  Then you can still take advantage of the ByteOrder of a ByteBuffer.

And the resulting code would have been... better?

[pjt33]

Indeed. Me lazy.

BMP and PNG (RGB24/ARGB32) are trivial. JPG not so simple. JAI did not do it (dispite the promise), and I didn't want to spend more time on it, so this was a quick hack, that will probably be used for a few years.

JAI does it for TIFFs - I've used it to process a 22k x 22k image without exceeding 64MB heap. Not sure how you were going about it, but what I used was

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ImageReader ir=ImageIO.getImageReadersByFormatName("tiff").next(); // Hacky ImageInputStream iis=new FileImageInputStream(new RandomAccessFile(file,"r")); ir.setInput(iis); for (y) {     for (x) {         ImageReadParam irp=new ImageReadParam();         irp.setSourceRegion(new Rectangle(x,y,w,h));         BufferedImage bi=ir.read(0,irp);         // Do stuff with bi     } }

If Sun's JPG reader doesn't handle that then there must be a third party one which does, although finding and getting it approved for use will, of course, be much hassle.

[Riven]

Thanks, turned out I used JAI totally different, and appearantly that resulted in loading the whole image.

Anyway, I got it to work with JPG (trivial, with your code sample), but man.. it's slow!


the image is 8K*4K

ImageIO.read(new File("something.jpg")); // 3sec

the code below takes almost 40 (!!) seconds. Just the loading of the tiles, not even scaling! So I'm going to stick with my current (external JVM) solution.

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ImageReader ir = ImageIO.getImageReadersByFormatName("jpeg").next();       ImageInputStream iis = new FileImageInputStream(new RandomAccessFile(file, "r"));       ir.setInput(iis);       int w = ir.getWidth(0);       int h = ir.getHeight(0);       int dim = 512;       for (int y = 0; y < h - dim; y += dim)       {          for (int x = 0; x < w - dim; x += dim)          {             ImageReadParam irp = new ImageReadParam();             irp.setSourceRegion(new Rectangle(x, y, dim, dim));             BufferedImage bi = ir.read(0, irp);             bi.flush();          }       }