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From: Fred Greer <fggreer@nospam.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: ImageIO/BufferedImage behaving inconsistently from one day to the next.
Date: Thu, 21 Jun 2012 04:58:46 +0000 (UTC)
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On Wed, 20 Jun 2012 21:23:35 -0700, Knute Johnson wrote:

> On 6/20/2012 5:23 PM, Fred Greer wrote:
>> 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.