Graphics.UI.Gtk.Gdk.Pixbuf

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.

Class Hierarchy

| GObject
| +----Pixbuf

Types

data Pixbuf

Instances

Eq Pixbuf

Ord Pixbuf

GObjectClass Pixbuf

PixbufClass Pixbuf

class GObjectClass o => PixbufClass o

Instances

PixbufClass Pixbuf

castToPixbuf :: GObjectClass obj => obj -> Pixbuf

gTypePixbuf :: GType

toPixbuf :: PixbufClass o => o -> Pixbuf

data PixbufError

Error codes for loading image files.

Constructors

PixbufErrorCorruptImage

PixbufErrorInsufficientMemory

PixbufErrorBadOption

PixbufErrorUnknownType

PixbufErrorUnsupportedOperation

PixbufErrorFailed

Instances

Enum PixbufError

GErrorClass PixbufError

data Colorspace

Enumerate all supported color spaces.

• Only RGB is supported right now.

Constructors

ColorspaceRgb

Instances

Enum Colorspace

Constructors

pixbufNew :: Colorspace -> Bool -> Int -> Int -> Int -> IO Pixbuf

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.

pixbufNewFromData :: Ptr CUChar -> Colorspace -> Bool -> Int -> Int -> Int -> Int -> IO Pixbuf

pixbufNewFromFile :: GlibFilePath fp => fp -> IO Pixbuf

Load an image synchonously.

• Use this function to load only small images as this call will block.
• If an error occurs, the function will throw an exception that can be caught using e.g. catchGErrorJust and one of the error codes in PixbufError.

pixbufNewFromFileAtSize :: GlibString string => string -> Int -> Int -> IO Pixbuf

Creates a new pixbuf by loading an image from a file. The file format is detected automatically. The image will be scaled to fit in the requested size, preserving the image's aspect ratio.

• If an error occurs, the function will throw an exception that can be caught using e.g. catchGErrorJust and one of the error codes in PixbufError.
• Available since Gtk+ version 2.4

pixbufNewFromFileAtScale

Arguments

:: GlibString string

=> string

the name of the file

-> Int

target width

-> Int

target height

-> Bool

whether to preserve the aspect ratio

-> IO Pixbuf

Creates a new pixbuf by loading an image from a file. The file format is detected automatically. The image will be scaled to fit in the requested size, optionally preserving the image's aspect ratio.

When preserving the aspect ratio, a width of -1 will cause the image to be scaled to the exact given height, and a 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. Negative values for width and height are allowed since Gtk+ 2.8.

• If an error occurs, the function will throw an exception that can be caught using e.g. catchGErrorJust and one of the error codes in PixbufError.
• Available since Gtk+ version 2.6

pixbufNewFromSurface :: Surface -> Int -> Int -> Int -> Int -> IO Pixbuf

Creates a new pixbuf from a cairo Surface.

Transfers image data from a cairo Surface and converts it to an RGB(A) representation inside a Pixbuf. This allows you to efficiently read individual pixels from cairo surfaces. For GdkWindows, use gdk_pixbuf_get_from_window() instead.

This function will create an RGB pixbuf with 8 bits per channel. The pixbuf will contain an alpha channel if the surface contains one.

pixbufNewFromInline :: Ptr InlineImage -> IO Pixbuf

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.

data InlineImage

A dymmy type for inline picture data.

• This dummy type is used to declare pointers to image data that is embedded in the executable. See pixbufNewFromInline for an example.

pixbufNewSubpixbuf :: Pixbuf -> Int -> Int -> Int -> Int -> IO Pixbuf

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.

pixbufNewFromXPMData :: GlibString string => [string] -> IO Pixbuf

Create a new image from a string.

• Creates a new pixbuf from a string description.

Methods

pixbufGetColorSpace :: Pixbuf -> IO Colorspace

Queries the color space of a pixbuf.

pixbufGetNChannels :: Pixbuf -> IO Int

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.

pixbufGetHasAlpha :: Pixbuf -> IO Bool

Query if the image has an alpha channel.

• The alpha channel determines the opaqueness of the pixel.

pixbufGetBitsPerSample :: Pixbuf -> IO Int

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.

data PixbufData i e

An array that stored the raw pixel data of a Pixbuf.

• See pixbufGetPixels.

Instances

Storable e => MArray PixbufData e IO

PixbufData is a mutable array.

pixbufGetPixels :: Storable e => Pixbuf -> IO (PixbufData Int e)

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 which have the same type signatures as readArray and writeArray. Note that these are internal functions that might change with GHC.

pixbufGetWidth :: Pixbuf -> IO Int

Queries the width of this image.

pixbufGetHeight :: Pixbuf -> IO Int

Queries the height of this image.

pixbufGetRowstride :: Pixbuf -> IO Int

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.

pixbufGetOption :: GlibString string => Pixbuf -> string -> IO (Maybe string)

Returns an attribut of an image.

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

type ImageFormat = DefaultGlibString

A string representing an image file format.

pixbufGetFormats :: [ImageFormat]

pixbufSave :: (GlibString string, GlibFilePath fp) => Pixbuf -> fp -> ImageFormat -> [(string, string)] -> IO ()

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.
• If an error occurs, the function will throw an exception that can be caught using e.g. catchGErrorJust and one of the error codes in PixbufError.

pixbufCopy :: Pixbuf -> IO Pixbuf

Create a deep copy of an image.

data InterpType

How an image is scaled.

InterpNearest

Nearest neighbor sampling; this is the fastest and lowest quality mode. Quality is normally unacceptable when scaling down, but may be OK when scaling up.

InterpTiles

This is an accurate simulation of the PostScript image operator without any interpolation enabled. Each pixel is rendered as a tiny parallelogram of solid color, the edges of which are implemented with antialiasing. It resembles nearest neighbor for enlargement, and bilinear for reduction.

InterpBilinear

Best quality/speed balance; use this mode by default. Bilinear interpolation. For enlargement, it is equivalent to point-sampling the ideal bilinear-interpolated image. For reduction, it is equivalent to laying down small tiles and integrating over the coverage area.

InterpHyper

This is the slowest and highest quality reconstruction function. It is derived from the hyperbolic filters in Wolberg's "Digital Image Warping", and is formally defined as the hyperbolic-filter sampling the ideal hyperbolic-filter interpolated image (the filter is designed to be idempotent for 1:1 pixel mapping).

Constructors

InterpNearest

InterpTiles

InterpBilinear

InterpHyper

Instances

Enum InterpType

pixbufScaleSimple

Arguments

:: Pixbuf

src - the source image

-> Int

width - the target width

-> Int

height the target height

-> InterpType

interpolation type

-> IO Pixbuf

Scale an image.

• Creates a new Pixbuf 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.

pixbufScale

Arguments

:: Pixbuf

src - the source pixbuf

-> Pixbuf

dest - the pixbuf into which to render the results

-> Int

destX - the left coordinate for region to render

-> Int

destY - the top coordinate for region to render

-> Int

destWidth - the width of the region to render

-> Int

destHeight - the height of the region to render

-> Double

offsetX - the offset in the X direction (currently rounded to an integer)

-> Double

offsetY - the offset in the Y direction (currently rounded to an integer)

-> Double

scaleX - the scale factor in the X direction

-> Double

scaleY - the scale factor in the Y direction

-> InterpType

the interpolation type for the transformation.

-> IO ()

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.

pixbufComposite

Arguments

:: Pixbuf

src - the source pixbuf

-> Pixbuf

dest - the pixbuf into which to render the results

-> Int

destX - the left coordinate for region to render

-> Int

destY - the top coordinate for region to render

-> Int

destWidth - the width of the region to render

-> Int

destHeight - the height of the region to render

-> Double

offsetX - the offset in the X direction (currently rounded to an integer)

-> Double

offsetY - the offset in the Y direction (currently rounded to an integer)

-> Double

scaleX - the scale factor in the X direction

-> Double

scaleY - the scale factor in the Y direction

-> InterpType

the interpolation type for the transformation.

-> Word8

alpha - the transparency

-> IO ()

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.

pixbufFlipHorizontally :: Pixbuf -> IO Pixbuf

Flips a pixbuf horizontally and returns the result in a new pixbuf.

pixbufFlipHorazontally :: Pixbuf -> IO Pixbuf

pixbufFlipVertically :: Pixbuf -> IO Pixbuf

Flips a pixbuf vertically and returns the result in a new pixbuf.

pixbufRotateSimple :: Pixbuf -> PixbufRotation -> IO Pixbuf

Rotates a pixbuf by a multiple of 90 degrees, and returns the result in a new pixbuf.

data PixbufRotation

The possible rotations which can be passed to pixbufRotateSimple.

To make them easier to use, their numerical values are the actual degrees.

Constructors

PixbufRotateNone

PixbufRotateCounterclockwise

PixbufRotateUpsidedown

PixbufRotateClockwise

Instances

Enum PixbufRotation

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.

pixbufAddAlpha :: Pixbuf -> Maybe (Word8, Word8, Word8) -> IO Pixbuf

pixbufCopyArea

Arguments

:: Pixbuf

Source pixbuf

-> Int

Source X coordinate within the source pixbuf

-> Int

Source Y coordinate within the source pixbuf

-> Int

Width of the area to copy

-> Int

Height of the area to copy

-> Pixbuf

Destination pixbuf

-> Int

X coordinate within the destination pixbuf

-> Int

Y coordinate within the destination pixbuf

-> IO ()

Copy a rectangular portion into another Pixbuf.

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

pixbufFill :: Pixbuf -> Word8 -> Word8 -> Word8 -> Word8 -> IO ()

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.