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§2.8 Class PixelGrabber
public class java.awt.image.PixelGrabber
extends java.lang.Object (I-§1.12)
implements java.awt.image.ImageConsumer (II-§2.10)
{
// Constructors
public PixelGrabber(Image img, int x, int y, §2.8.1
int w, int h, int pix[], int off, int scansize);
public PixelGrabber(ImageProducer ip, int x, §2.8.2
int y, int w, int h, int pix[], int off, int scansize);
// Methods
public boolean grabPixels(); §2.8.3
public boolean grabPixels(long ms); §2.8.4
public void imageComplete(int status); §2.8.5
public void setColorModel(ColorModel model); §2.8.6
public void setDimensions(int width, int height) §2.8.7
public void setHints(int hints); §2.8.8
public void setPixels(int srcX, int srcY, int srcW, §2.8.9
int srcH, ColorModel model,
byte pixels[], int srcOff, int srcScan);
public void setPixels(int srcX, int srcY, int srcW, §2.8.10
int srcH, ColorModel model,
int pixels[], int srcOff, int srcScan);
public void setProperties(Hashtable props); §2.8.11
public int status(); §2.8.12
}
The pixel grabber implements an image consumer which can be attached to an image or
image producer object to retrieve a subset of the pixels in that image. Pixels are stored in
the array in the default RGB color model (II-§2.1.9).
For example:
public void handleSinglePixel(int x, int y, int pixel) {
int alpha = (pixel >> 24) & 0xff;
int red = (pixel >> 16) & 0xff;
int green = (pixel >> 8) & 0xff;
int blue = (pixel ) & 0xff;
// Deal with the pixel as necessary...
}
public void GetPixels(Image img, int x, int y, int w, int h) {
int[] pixels = new int[w * h];
PixelGrabber pg =
new PixelGrabber(img, x, y, w, h, pixels, 0, w);
try {
pg.grabPixels();
} catch (InterruptedException e) {
System.err.println("interrupted waiting for pixels!");
return;
}
if ((pg.status() & ImageObserver.ABORT) != 0) {
System.err.println("image fetch aborted or errored");
return;
}
for (int j = 0; j < h; j++) {
for (int i = 0; i < w; i++) {
// look at the pixel
handleSinglePixel(x+i, y+j, pixels[j * w + i]);
}
}
}
Most applications need to call only the grabPixel methods (§2.8.3, §2.8.4) and the status
method (II-§2.8.12) of this class. The remaining methods are part of the ImageConsumer
interface and allow the pixel grabber to receive the image from the image producer.
PixelGrabber
public PixelGrabber(Image img, int x, int y, int w, int h,
int pix[], int off, int scansize)
- Creates a new pixel grabber object to grab the rectangular section of pixels
from the specified image into the specified array.
- The pixels are stored in the array in the default RGB color model
(II-§2.1.9). The pixel data for the coordinate
, where
is inside
the indicted rectangle, is stored in the array at index
- of the pixel array.
- The x and y coordinates indicate the upper left corner of the rectangle of
pixels to retrieve from the image, relative to the default (unscaled) size of
the image.
- Parameters:
img
- the image from which to retrieve pixels
x
- the x coordinate of the upper left corner
y
- the y coordinate of the upper left corner
w
- the width of the rectangle to retrieve
h
- the height of the rectangle to retrieve
pix
- the array of integers into which to place the RGB pixels retrieved
from the image
off
- the offset into the array to store the first pixel
scansize
- the distance from the start of one row of pixels to the start of
the next row in the array
PixelGrabber
public PixelGrabber(ImageProducer ip, int x, int y,
int w, int h, int pix[],
int off, int scansize)
- Creates a new pixel grabber object to grab the rectangular section of pixels
from the specified image producer into the specified array.
- The pixels are stored in the array in the default RGB color model
(II-§2.1.9). The pixel data for the coordinate
, where
is inside
the indicted rectangle, is stored in the array at the index
- of the pixel array.
- The x and y coordinates indicate the upper left corner of the rectangle of
pixels to retrieve from the image, relative to the default (unscaled) size of
the image.
- Parameters:
ip
- the image producer
x
- the x coordinate of the upper left corner
y
- the y coordinate of the upper left corner
w
- the width of the rectangle to retrieve
h
- the height of the rectangle to retrieve
pix
- the array of integers into which to place the RGB pixels retrieved
from the image
off
- the offset into the array to store the first pixel
scansize
- the distance from the start of one row of pixels to the start of
the next row in the array
grabPixels
public boolean grabPixels()
throws InterruptedException
- Requests the image or image producer to start delivering pixels to this
image consumer. It waits for all of the pixels in the rectangle of interest to
be delivered.
- Returns:
- true if the pixels were successfully grabbed; false on abort or error.
- Throws
- InterruptedException (I-§1.37)
- If another thread has interrupted this thread.
grabPixels
public boolean grabPixels(long ms)
throws InterruptedException
- Requests the image or image producer to start delivering pixels to this
image consumer. It waits for all of the pixels in the rectangle of interest to
be delivered, or until the specified timeout has elapsed.
- Parameters:
ms
- the number of milliseconds to wait for the pixels
- Returns:
- true if the pixels were successfully grabbed; false on abort, error or timeout.
- Throws
- InterruptedException (I-§1.37)
- If another thread has interrupted this thread.
imageComplete
public void imageComplete(int status)
- The image producer calls the imageComplete method when it has completed
an image or it has errored in producing or loading the image. For more
information on this method and its status argument, see §2.10.10 on
page 304.
- The imageComplete method of PixelGrabber notifies all processes waiting for
the pixels to wake up. It uses the value of the status flag to determine
whether the image was successfully retrieved or not.
- Parameters:
status
- the status of the image
setColorModel
public void setColorModel(ColorModel model)
- The image producer calls the setColorModel method to specify the color
model for the majority of the subsequent setPixels method calls. For more
information on this method and its model argument, see §2.10.11 on
page 305
- The setColorModel method of PixelGrabber ignores this call.
- Parameters:
model
- a color map used in subsequent setPixel calls
setDimensions
public void setDimensions(int width, int height)
- The image producer calls the setDimensions of the image consumer to tell it
the width and height of the image.
- The setDimensions method of PixelGrabber ignores the dimensions.
- Parameters:
width
- the width of the image
height
- the height of the image
setHints
public void setHints(int hints)
- The image producer calls the setHints method of the image consumer to
indicate the order in which the bits will be delivered. For more information
on the hints passed to the image consumer, see §2.10.13 on page 306.
- The setHints method of PixelGrabber ignores the hints.
- Parameters:
hints
- hints about the order in which the bits will be delivered
setPixels
public void
setPixels(int srcX, int srcY, int srcW, int srcH,
ColorModel model, byte pixels[],
int srcOff, int srcScan)
- The image producer calls the setPixels method of the image consumer one
or more times to deliver the pixels of the image. For more information on
this method and its arguments, see §2.10.14 on page 307.
- The setPixels method of PixelGrabber places the bits, if appropriate, into the
array of bits passed to it by a call to the grabPixels method (II-§2.8.3).
- Parameters:
x
- left coordinate of rectangle
y
- top coordinte of rectangle
w
- width of rectangle
h
- height of rectangle
model
- color model for bits
pixels
- array of bits
off
- offset for first element
scansize
- number of elements per row
setPixels
public void
setPixels(int srcX, int srcY, int srcW, int srcH,
ColorModel model, int pixels[],
int srcOff, int srcScan)
- The image producer calls the setPixels method of the image consumer one
or more times to deliver the pixels of the image. For more information on
this method and its arguments, see §2.10.15 on page 308.
- The setPixels method of PixelGrabber places the bits, if appropriate, into the
array of bits passed to it by a call to the grabPixels method (II-§2.8.3).
- Parameters:
x
- left coordinate of rectangle
y
- top coordinte of rectangle
w
- width of rectangle
h
- height of rectangle
model
- color model for bits
pixels
- array of bits
off
- offset for first element
scansize
- number of elements per row
setProperties
public void setProperties(Hashtable props)
- The image producer calls the setProperties method of the image consumer to
let it know of additional properties of the image. For more information on
this method and its arguments, see §2.10.16 on page 308.
- The setPropertiess method of PixelGrabber ignores the hints.
- Parameters:
props
- a hashtable that maps image properties to their value
status
public int status()
- Returns the bitwise OR of the appropriate ImageObserver interface
(II-§2.11) flags.
- Returns:
- the status of the pixels.
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