Load images - new thread - Processing Forum

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Psysoul

Load images - new thread

in Programming Questions • 2 years ago

I am trying to load flickr images in a new thread using this:

http://wiki.processing.org/w/Asynchronous_data/image_loading

I deleted the caching, because I don't need it, someone also posted the code without caching here: ( p5wiki_async_loader )

http://learn.postspectacular.com/hg/

Problem is that I get this error:

java.lang.ClassCastException: [I cannot be cast to [B

Code is in databuffer class, around line 40: return new PImage(bimg);

What might be the problem?

Images are loaded and I can save them using saveBytes("test.jpg",bytes);

Copy code

public PImage getAsImage() {
try {
ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
BufferedImage bimg = ImageIO.read(bis);
return new PImage(bimg);
} catch (Exception e) {
println(e);
System.err.println("Can't create image from buffer");
}
return null;
}

Replies(2)

PhiLho

If I recall correctly, a similar question have been asked recently.
The semi-cryptic error message means a method is fed with an array of int [I ([ is for array, I is for int) while the method was expecting an array of bytes [B.
The array of integers is created inside the PImage constructor you call: it tries to extract the data from the BufferedImage into the pixels[] array, but fails because of incompatible data format.

Psysoul

Re: Load images - new thread

2 years ago

Thanks, this makes a bit more sense, so I managed to get this working in a way:

The problem was that raster.getDataElements will use an array type of Transfertype which turned out to be byte[] instead of int[].

getDataElements:

"Returns the pixel data for the specified rectangle of pixels in a primitive array of type TransferType. For image data supported by the Java 2D API, this will be one of DataBuffer.TYPE_BYTE, DataBuffer.TYPE_USHORT, DataBuffer.TYPE_INT, DataBuffer.TYPE_SHORT, DataBuffer.TYPE_FLOAT, or DataBuffer.TYPE_DOUBLE"

So instead I am using raster.getPixels(0, 0, width, height, mypixels); which will fill mypixels int[] with our values. Then I can create an image using those pixels.

Also the int[] needs to be width*height*3 because we use RGB, so 8-8-8 bits for RGB values.

I am not sure this problem lies within processings PImage constructor, or the original program on the wiki site...

Is there a better solution? Maybe use an IntArrayInput stream or something..? I am not really into pure Java.

Solution:

Copy code

ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
BufferedImage bimg = ImageIO.read(bis);
int[] mypixels;
//byte[] mybyte;
width = bimg.getWidth();
height = bimg.getHeight();
mypixels = new int[width * height * 3];
//mybyte = new byte[width * height];
WritableRaster raster = bimg.getRaster();
//raster.getDataElements(0, 0, width, height, mybyte );
raster.getPixels(0, 0, width, height, mypixels);
PImage img = createImage(width, height, RGB);
img.loadPixels();
for (int i = 0; i < (width * height); i++) {
img.pixels[i] = color(mypixels[ (3*i)], mypixels[(3*i + 1) ], mypixels[(3*i +2) ]);
}
img.updatePixels();
return img;

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