Pixbufs are bitmap images in memory.

• A Pixbuf is used to represent images. It contains information about the image's pixel data, its color space, bits per sample, width and height, and the rowstride or number of bytes between rows.
• This module contains functions to scale and crop Pixbufs and to scale and crop a Pixbuf and compose the result with an existing image.
• Pixbufs can be displayed on screen by either creating an Image that from the Pixbuf or by rendering (part of) the Pixbuf into a vanilla widget like DrawWindow using drawPixbuf.

Queries the number of colors for each pixel.

• This function returns 3 for an RGB image without alpha (transparency) channel, 4 for an RGB image with alpha channel.

Query if the image has an alpha channel.

• The alpha channel determines the opaqueness of the pixel.

Queries the number of bits for each color.

• Each pixel is has a number of cannels for each pixel, each channel has this many bits.

Retrieve the internal array of raw image data.

• Image data in a pixbuf is stored in memory in uncompressed, packed format. Rows in the image are stored top to bottom, and in each row pixels are stored from left to right. There may be padding at the end of a row. The rowstride value of a pixbuf, as returned by pixbufGetRowstride, indicates the number of bytes between rows.
• The returned array is a flat representation of a three dimensional array: x-coordiante, y-coordinate and several channels for each color. The number of channels is usually 3 for plain RGB data or 4 for RGB data with an alpha channel. To read or write a specific pixel use the formula: p = y * rowstride + x * nChannels for the pixel. If the array contains bytes (or Word8s), p+0 is the red value, p+1 green, p+2 blue and p+3 the alpha (transparency) channel if present. If the alpha channel is present, the array can accessed as an array over Word32 to modify a whole pixel at a time. See also pixbufGetBitsPerSample and pixbufGetNChannels.
• Calling this function without explicitly giving it a type will often lead to a compiler error since the type parameter e is underspecified. If this happens the function can be explicitly typed: pbData <- (pixbufGetPixels pb :: IO (PixbufData Int Word8))
• If modifying an image through Haskell's array interface is not fast enough, it is possible to use unsafeRead and unsafeWrite from Data.Array.Base which have the same type signatures as readArray and writeArray. Note that these are internal functions that might change with GHC.

Queries the rowstride of this image.

• Queries the rowstride of a pixbuf, which is the number of bytes between rows. Use this value to caculate the offset to a certain row.

Returns an attribut of an image.

• Looks up if some information was stored under the key when this image was saved.

Load an image synchonously.

• Use this function to load only small images as this call will block.
• The function will return Left (err,msg) where err is the error code and msg is a human readable description of the error. If an error occurs which is not captured by any of those in PixbufError, an exception is thrown.

Save an image to disk.

• The function takes a list of key - value pairs to specify either how an image is saved or to actually save this additional data with the image. JPEG images can be saved with a "quality" parameter; its value should be in the range [0,100]. Text chunks can be attached to PNG images by specifying parameters of the form "tEXt::key", where key is an ASCII string of length 1-79. The values are Unicode strings.
• The function returns Nothing if writing was successful. Otherwise the error code and a description is returned or, if the error is not captured by one of the error codes in PixbufError, an exception is thrown.

Create a new image in memory.

• Creates a new pixbuf structure and allocates a buffer for it. Note that the buffer is not cleared initially.
• The boolean flag is true if the pixbuf should have an alpha (transparency) channel. The next integer denotes the bits per color sample, e.g. 8 bits per color for 2^24 colors. The last two integers denote the width and height, respectively.

Create a new image from a String.

• Creates a new pixbuf from a string description.

Create a new image from a static pointer.

• Like pixbufNewFromXPMData, this function allows to include images in the final binary program. The method used by this function uses a binary representation and therefore needs less space in the final executable. Save the image you want to include as png and run:

 @echo #include "my_image.h" > my_image.c
 gdk-pixbuf-csource --raw --extern --name=my_image myimage.png >> my_image.c

on it. Write a header file my_image.h containing:

 #include <gdk/gdk.h>
 extern guint8 my_image[];

and save it in the current directory. The created file can be compiled with:

 cc -c my_image.c `pkg-config --cflags gdk-2.0`

into an object file which must be linked into your Haskell program by specifying my_image.o and "-#include my_image.h" on the command line of GHC. Within you application you delcare a pointer to this image:

 foreign label "my_image" myImage :: Ptr InlineImage

Calling pixbufNewFromInline with this pointer will return the image in the object file. Creating the C file with the --raw flag will result in a non-compressed image in the object file. The advantage is that the picture will not be copied when this function is called.

Create a restricted view of an image.

• This function returns a Pixbuf object which shares the image of the original one but only shows a part of it. Modifying either buffer will affect the other.
• This function throw an exception if the requested bounds are invalid.

Scale an image.

• Creates a new GdkPixbuf containing a copy of src scaled to the given measures. Leaves src unaffected.
• interp affects the quality and speed of the scaling function. InterpNearest is the fastest option but yields very poor quality when scaling down. InterpBilinear is a good trade-off between speed and quality and should thus be used as a default.

Copy a scaled image part to another image.

• This function is the generic version of pixbufScaleSimple. It scales src by scaleX and scaleY and translate the image by offsetX and offsetY. Whatever is in the intersection with the rectangle destX, destY, destWidth, destHeight will be rendered into dest.
• The rectangle in the destination is simply overwritten. Use pixbufComposite if you need to blend the source image onto the destination.

Blend a scaled image part onto another image.

• This function is similar to pixbufScale but allows the original image to "shine through". The alpha value determines how opaque the source image is. Passing 0 is equivalent to not calling this function at all, passing 255 has the same effect as calling pixbufScale.

Add an opacity layer to the Pixbuf.

• This function returns a copy of the given src Pixbuf, leaving src unmodified. The new Pixbuf has an alpha (opacity) channel which defaults to 255 (fully opaque pixels) unless src already had an alpha channel in which case the original values are kept. Passing in a color triple (r,g,b) makes all pixels that have this color fully transparent (opacity of 0). The pixel color itself remains unchanged during this substitution.

Copy a rectangular portion into another Pixbuf.

• The source Pixbuf remains unchanged. Converion between different formats is done automatically.

Fills a Pixbuf with a color.

• The passed-in color is a quadruple consisting of the red, green, blue and alpha component of the pixel. If the Pixbuf does not have an alpha channel, the alpha value is ignored.

Take a screenshot of a Drawable.

• This function creates a Pixbuf and fills it with the image currently in the Drawable (which might be invalid if the window is obscured or minimized). Note that this transfers data from the server to the client on X Windows.
• This function will return a Pixbuf with no alpha channel containing the part of the Drawable specified by the rectangle. The function will return Nothing if the window is not currently visible.