ImageIO/BufferedImage behaving inconsistently from one day to thenext.


F

Fred Greer

I have code that used to work perfectly, which processes images in
certain ways, and today it suddenly was not working. I hadn't changed the
code at all. I tracked the problem down to spurious
IllegalArgumentExceptions being thrown by this code:

public class ImageUtils {

private static float[] BLUR = {0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111}
....
public static BufferedImage blur (BufferedImage img) {
Kernel k = new Kernel(3, 3, BLUR);
ConvolveOp co = new ConvolveOp(k, ConvolveOp.EDGE_NO_OP, null);
BufferedImage dest = new BufferedImage(img.getWidth(),
img.getHeight(),img.getType());
co.filter(img,dest);
return dest;
}
....
}

This code worked yesterday and fails today with

java.lang.IllegalArgumentException: Unknown image type 0

and a stack trace pointing to the line creating dest.

I did some fiddling, and when loading any PNG image with ImageIO.read,
the result (after being fed through something that uses reflection to try
to identify bean-like properties in order to "inspect" an object; one of
my debugging tools) is this:

java.awt.image.BufferedImage: type = 0 ColorModel: #pixelBits = 32
numComponents = 4 color space = [email protected]
transparency = 3 has alpha = true isAlphaPre = false
ByteInterleavedRaster: width = 2560 height = 1440 #numDataElements 4
dataOff[0] = 0

According to the Javadocs, a type of 0 represents "Custom".

There are only two conclusions to draw from this:

1. Overnight, BufferedImage suddenly stopped accepting a type of 0, or
2. Overnight, ImageIO.read suddenly started setting the image type to 0
instead of something more specific like TYPE_INT_ARGB when loading and
decoding PNGs.

Neither of these makes much sense, because standard library code is not
supposed to magically change its behavior like that, and it's certainly
not supposed to make something that used to work no longer work by
magically changing its behavior overnight.

Now, when I first wrote the blur method it had had

BufferedImage dest = co.createCompatibleDestImage(img,
img.getColorModel());

instead. The result had been a blank black image output from
ImageUtils.blur(foo) no matter what the input looked like. I've now tried
that again, and suddenly it works.

So, literally overnight and without apparent provocation,

new BufferedImage(img.getWidth(),img.getHeight(),img.getType())

magically started throwing exceptions when it used to work with the exact
same disk file loaded into img in the exact same way, and at the same
time,

co.createCompatibleDestImage(img,img.getColorModel());

magically started *working* when it had previously created destination
images that didn't actually work with the ConvolveOp in question, despite
the obvious contract of the method named "createCompatibleDestImage".

Can anyone explain these occurrences?

Furthermore, can anyone suggest an implementation of blur that is
guaranteed not only to work, but to stay working in perpetuity and not
magically stop working some day? What if the version of blur using
createCompatibleDestImage suddenly goes back to producing blank images? I
can restore the other version of the code. Or I can even write

try {
; Blur implementation using constructor and .getType goes here
} catch (IllegalArgumentException x) {
; Blur implementation using createCompatibleDestImage goes here
}

and this will presumably work even if it randomly toggles between the two
observed patterns of behavior every Tuesday and alternate Thursday,
though it'll be an evil, ugly hack. But what if it suddenly jumps to some
*third* state where *neither* implementation of blur works and I have to
try something completely new? And what if it changes to something
unprecedented again after that, and again, and every week forever?

Logically, that shouldn't be possible. But by the same logic *what I've
already observed* shouldn't be possible, so obviously that logic is
suspect and I can no longer assume that blur needing a completely novel
implementation every week, or every day, or even every hour cannot
happen. Doctors needing completently novel antibiotics to treat staph
infections not only can but has happened, and happened repeatedly, after
all, so if something in the JVM has started "evolving resistance" to
blurring images successfully, for some reason, then the same thing could
happen there.

So, is there something that is evolving or changing under the hood in how
ImageIO/AWT operates? And if so, are there any rock-stable guarantees
regarding the API behavior that I can rely on to implement a blur method
that will never fail for any valid input image? I'd have thought, from
reading the javadocs for it, that createCompatibleDestImage was it, but
that's already been disproved...
 
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F

Fred Greer

Can you upload the image someplace where we can access it? And then
download it again and verify it's the same as you have on your disc
drive, sometimes image services reduce resolution or compress images.

We will have a better shot at figuring something out if we have the
offending file to inspect.

I checked and the behavior change seems to affect all .png files
regardless of origin or what program generated them. I didn't check .jpg
or other formats.

Any .png should therefore be substitutable for any other in checking this
(except that the createCompatibleDestImage issue won't be detectable if
it's a blank black .png).
 
F

Fred Greer

On 6/19/2012 7:31 PM, Fred Greer wrote: ...

Is your code multi-threaded?

I'm asking because things that transition "magically" between working
and not working are often timing dependent, and transition because of a
change that affects relative speeds, such as file placement and cache
history.

Patricia

It's single-threaded.
 
R

Roedy Green

(BufferedImage img
did you put in MediaTracker wait code for this to load? If you
didn't sometimes you will try to get the size before it loads.
--
Roedy Green Canadian Mind Products
http://mindprod.com
If you look in a computer programmer's freezer you will find all
kinds of containers, but none of them labeled. They do the same thing
creating files without labeling the encoding. You are just supposed to
know. Ditto with the MIME type, the separator and comment delimiters and
column names in CSV files. Ditto with the endian convention. Imagine how
much more civilised life would have been if Martha Stewart were the first
programmer.
 
J

Joerg Meier

did you put in MediaTracker wait code for this to load? If you
didn't sometimes you will try to get the size before it loads.

I'm with Roedy, especially if the situation changed without you doing
anything to the code, I would suspect it to be a timing issue with the
image loading. You haven't show the image loading code, so it's hard to
tell, but try to insert after

public static BufferedImage blur (BufferedImage img) {

a line like

Toolkit.getDefaultToolkit().prepareImage(img, -1, -1, new ImageObserver());

before you try to use the image.

I don't recall off hand, and you'll have to do your own research, but I
think you can just pass null instead of an actual ImageObserver, and of
course this code should really go to where the image is actually loaded.

Liebe Gruesse,
Joerg
 
K

Knute Johnson

I have code that used to work perfectly, which processes images in
certain ways, and today it suddenly was not working. I hadn't changed the
code at all. I tracked the problem down to spurious
IllegalArgumentExceptions being thrown by this code:

public class ImageUtils {

private static float[] BLUR = {0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111}
...
public static BufferedImage blur (BufferedImage img) {
Kernel k = new Kernel(3, 3, BLUR);
ConvolveOp co = new ConvolveOp(k, ConvolveOp.EDGE_NO_OP, null);
BufferedImage dest = new BufferedImage(img.getWidth(),
img.getHeight(),img.getType());

Please try just putting BufferedImage.TYPE_INT_ARGB here instead of
getting the type from the other image and tell us what happens.
 
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J

John B. Matthews

I have code that used to work perfectly, which processes images in
certain ways, and today it suddenly was not working. I hadn't
changed the code at all. I tracked the problem down to spurious
IllegalArgumentExceptions being thrown by this code:
[...]
So this is the code you say isn't working? It works for me:


package quicktest;

import java.awt.image.BufferedImage;
import java.awt.image.ConvolveOp;
import java.awt.image.Kernel;
import javax.imageio.ImageIO;

/**
*
* @author Brenden
*/
public class ConvlPng {

public static void main(String[] args)
throws Exception
{
BufferedImage png = ImageIO.read(
ConvlPng.class.getResourceAsStream( "conv_test.png" ) );
BufferedImage conv = blur( png );
System.out.println( conv );
}


private static float[] BLUR = {0.1111111f, 0.1111111f, 0.1111111f,
0.1111111f, 0.1111111f, 0.1111111f,
0.1111111f, 0.1111111f, 0.1111111f};

public static BufferedImage blur (BufferedImage img) {
Kernel k = new Kernel(3, 3, BLUR);
ConvolveOp co = new ConvolveOp(k, ConvolveOp.EDGE_NO_OP, null);
BufferedImage dest = new BufferedImage(img.getWidth(),
img.getHeight(),img.getType());
co.filter(img,dest);
return dest;
}
}

I couldn't resist adding a GUI:

<https://sites.google.com/site/trashgod/convolution>

and taking a picture:

<https://sites.google.com/site/trashgod/_/rsrc/1340216139027/convolution/ConvlPng.png>
 
F

Fred Greer

did you put in MediaTracker wait code for this to load? If you
didn't sometimes you will try to get the size before it loads.

It's being loaded with ImageIO.read(), which so far as I have been able
to determine is synchronous. In fact I'm not sure a BufferedImage can
ever appear to calling code to not be not fully loaded (as opposed to a
generic Image).
 
F

Fred Greer

I have code that used to work perfectly, which processes images in
certain ways, and today it suddenly was not working. I hadn't changed
the code at all. I tracked the problem down to spurious
IllegalArgumentExceptions being thrown by this code:

public class ImageUtils {

private static float[] BLUR = {0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111}
...
public static BufferedImage blur (BufferedImage img) {
Kernel k = new Kernel(3, 3, BLUR);
ConvolveOp co = new ConvolveOp(k, ConvolveOp.EDGE_NO_OP,
null); BufferedImage dest = new BufferedImage(img.getWidth(),
img.getHeight(),img.getType());

Please try just putting BufferedImage.TYPE_INT_ARGB here instead of
getting the type from the other image and tell us what happens.

Are 32-bit PNGs loaded via ImageIO.read guaranteed to be ARGB, or at
least compatible with ARGB destination images for the purposes of
ConvolveOp and friends?
 
K

Knute Johnson

I have code that used to work perfectly, which processes images in
certain ways, and today it suddenly was not working. I hadn't changed
the code at all. I tracked the problem down to spurious
IllegalArgumentExceptions being thrown by this code:

public class ImageUtils {

private static float[] BLUR = {0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111}
...
public static BufferedImage blur (BufferedImage img) {
Kernel k = new Kernel(3, 3, BLUR);
ConvolveOp co = new ConvolveOp(k, ConvolveOp.EDGE_NO_OP,
null); BufferedImage dest = new BufferedImage(img.getWidth(),
img.getHeight(),img.getType());

Please try just putting BufferedImage.TYPE_INT_ARGB here instead of
getting the type from the other image and tell us what happens.

Are 32-bit PNGs loaded via ImageIO.read guaranteed to be ARGB, or at
least compatible with ARGB destination images for the purposes of
ConvolveOp and friends?

I am certainly no expert but I would think that a PNG file would create
an ARGB image without any problems and I was curious what would happen.

The other option is to not even create a new image and just convert the
one you have by putting null destination field.
 
F

Fred Greer

On 6/19/2012 7:31 PM, Fred Greer wrote:
I have code that used to work perfectly, which processes images in
certain ways, and today it suddenly was not working. I hadn't changed
the code at all. I tracked the problem down to spurious
IllegalArgumentExceptions being thrown by this code:

public class ImageUtils {

private static float[] BLUR = {0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111}
...
public static BufferedImage blur (BufferedImage img) {
Kernel k = new Kernel(3, 3, BLUR);
ConvolveOp co = new ConvolveOp(k, ConvolveOp.EDGE_NO_OP,
null); BufferedImage dest = new
BufferedImage(img.getWidth(),
img.getHeight(),img.getType());

Please try just putting BufferedImage.TYPE_INT_ARGB here instead of
getting the type from the other image and tell us what happens.

Are 32-bit PNGs loaded via ImageIO.read guaranteed to be ARGB, or at
least compatible with ARGB destination images for the purposes of
ConvolveOp and friends?

I am certainly no expert but I would think that a PNG file would create
an ARGB image without any problems and I was curious what would happen.

The other option is to not even create a new image and just convert the
one you have by putting null destination field.

I thought that didn't work, at least for some transformations? At the
same time, I prefer to minimize mutation and prefer creating new objects.
There's much less scope for concurrency problems and some other sorts of
bugs that way, particularly when a single object is used in various
places and none of them expect it to change because of one of the other
places.
 
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K

Knute Johnson

On Wed, 20 Jun 2012 08:39:37 -0700, Knute Johnson wrote:

On 6/19/2012 7:31 PM, Fred Greer wrote:
I have code that used to work perfectly, which processes images in
certain ways, and today it suddenly was not working. I hadn't changed
the code at all. I tracked the problem down to spurious
IllegalArgumentExceptions being thrown by this code:

public class ImageUtils {

private static float[] BLUR = {0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111,
0.1111111, 0.1111111, 0.1111111}
...
public static BufferedImage blur (BufferedImage img) {
Kernel k = new Kernel(3, 3, BLUR);
ConvolveOp co = new ConvolveOp(k, ConvolveOp.EDGE_NO_OP,
null); BufferedImage dest = new
BufferedImage(img.getWidth(),
img.getHeight(),img.getType());

Please try just putting BufferedImage.TYPE_INT_ARGB here instead of
getting the type from the other image and tell us what happens.

Are 32-bit PNGs loaded via ImageIO.read guaranteed to be ARGB, or at
least compatible with ARGB destination images for the purposes of
ConvolveOp and friends?

I am certainly no expert but I would think that a PNG file would create
an ARGB image without any problems and I was curious what would happen.

The other option is to not even create a new image and just convert the
one you have by putting null destination field.

I thought that didn't work, at least for some transformations? At the
same time, I prefer to minimize mutation and prefer creating new objects.
There's much less scope for concurrency problems and some other sorts of
bugs that way, particularly when a single object is used in various
places and none of them expect it to change because of one of the other
places.

All right then, that's all I've got for you.
 

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