org.gnome.gdk
Class Pixbuf

Object
  org.freedesktop.bindings.Pointer
      org.freedesktop.bindings.Proxy
          org.gnome.glib.Object
              org.gnome.gdk.Pixbuf

public class Pixbuf
extends Object

An image in memory.

Pixbuf is just here to be efficient at handling images that are going to placed in your GTK user interfaces. If you want to draw on an image, use Cairo's ImageSurface. If you want to otherwise manipulate the image, use a dedicated image processing library to load the data as it will doubtless provide for more efficient storage anticipating the processing tasks it will facilitate.

Since:

4.0.0

Author:

Andrew Cowie, Serkan Kaba

Pixbuf

public Pixbuf(byte[] data)
       throws IOException

Construct a new Pixbuf object from image data already in memory. The data needs to be a complete image in a format that will be recognized by one of the gdk-pixbuf library's loaders (PNG, JPEG, etc).

Throws:

IOException

Since:

4.0.10

Pixbuf

public Pixbuf(byte[] data,
              int width,
              int height,
              boolean preserveAspectRatio)
       throws IOException

Construct a new Pixbuf from in-memory data and scale it.

See Pixbuf(byte[]) for info on in-memory data.
See Pixbuf(String, int, int, boolean) for info on scaling.

Throws:

IOException

Since:

4.0.12

Pixbuf

public Pixbuf(int width,
              int height)

Pixbuf

public Pixbuf(String filename)
       throws FileNotFoundException

Construct a new Pixbuf object from the image found in filename.

Throws:

FileNotFoundException

Since:

4.0.5

Pixbuf

public Pixbuf(String filename,
              int width,
              int height,
              boolean preserveAspectRatio)
       throws FileNotFoundException

Construct a new Pixbuf object by loading an image from a given filename, but scaling it. The image will be scaled to fit the supplied width and height, preserving the aspect ratio or not based on the value of the fourth parameter.

If preserving the aspect ratio,

• width of -1 will cause the image to be scaled to the exact given height
• height of -1 will cause the image to be scaled to the exact given width.

When not preserving aspect ratio,

• a width or height of -1 means to not scale the image at all in that dimension.

Throws:

FileNotFoundException

Since:

4.0.5

copy

public Pixbuf copy()

Create an identical copy of this Pixbuf.

Since you can happily reuse a Pixbuf instance in multiple places, you generally won't need this unless doing mutating operations like rescaling.

Since:

4.0.10

getFileInfoHeight

public static int getFileInfoHeight(String filename)
                             throws IOException

Query an image on disk for its height.

This function is the compliment of getFileInfoWidth(); see there.

Throws:

IOException

Since:

4.0.14

getFileInfoWidth

public static int getFileInfoWidth(String filename)
                            throws IOException

Query an image on disk for its width.

This is a utility function where the minimum amount is read in order to determine metadata about the file in question. You'll get an IOException if the gdk-pixbuf library's image loaders can't figure out the format of the file.

Throws:

IOException

Since:

4.0.14

getHeight

public int getHeight()

Get the height of this Pixbuf, in pixels

Since:

4.0.8

getNumChannels

public int getNumChannels()

Get the number of colour channels in this Pixbuf. This will be either 3 for RGB or 4 for an RGBA image.

You don't actually need this; if you're working with the pixel data from getPixels() just divide the length of the returned array by (width * height).

Since:

4.0.8

getPixels

public byte[] getPixels()

Get a the individual pixel values comprising this Pixbuf.

Image data in a Pixbuf is stored in memory in an uncompressed but packed format. Rows in the image are stored top to bottom, and in each row pixels are stored from left to right. The returned array is, as you would expect, the bytes comprising each single pixel in a sequential series. There will be either three (RGB) or four (RGBA) bytes per pixel, see getNumChannels().

The return array is of type of is byte but you can expect unsigned values in the range 0 to 255. If you need the actual values you'll have to & with 0xFF to get yourself to the correct unsigned integer.

You should not need to call this. See the caveats at the top of this class; changing the values of this array will not change the underlying image.

The underlying library stores Pixbufs in a format which is efficient for internal representation and memory operations, though not necessarily efficient for size and frequently extra bits are added as alignment padding. We do some minor copying so that the array returned is one byte per channel and Cartesian.

In the current GDK Pixbuf library implementation, the red, green, blue and optional alpha are fixed at 8 bits per channel.

Since:

4.0.8

getWidth

public int getWidth()

Get the width of this Pixbuf, in pixels

Since:

4.0.8

save

public void save(String filename,
                 PixbufFormat type)

Write this Pixbuf to a file.

The various file formats that GDK is actually capable of writing to are specified by the constants on PixbufFormat. For example, you can save a screenshot as a PNG using:

 Pixbuf p;
 ...
 
 p.save("Screenshot.png", PixbufFormat.PNG);
 

Since:

4.0.5

scale

public Pixbuf scale(int width,
                    int height,
                    InterpType algorithm)

Create a new Pixbuf, applying the scaling factors inherent in the ratios between the size of this Pixbuf and the new image size specified by width and height.

In general you probably want to use the BILINEAR interpolation algorithm.

Since:

4.0.10

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