Images and Sprites¶
pyglet provides functions for loading and saving images in various formats using native operating system services. If the Pillow library is installed, many additional formats can be supported. pyglet also includes built-in codecs for loading PNG and BMP without external dependencies.
Loaded images can be efficiently provided to OpenGL as a texture, and OpenGL textures and framebuffers can be retrieved as pyglet images to be saved or otherwise manipulated.
If you’ve done any game or graphics programming, you’re probably familiar with
the concept of “sprites”. pyglet also provides an efficient and comprehensive
Sprite class, for displaying images on the screen
with an optional transform (such as scaling and rotation). If you’re planning
to do anything with images that involves movement and placement on screen,
you’ll likely want to use sprites.
Loading an image¶
Images can be loaded using the
kitten = pyglet.image.load('kitten.png')
If you are distributing your application with included images, consider
pyglet.resource module (see Application resources).
Without any additional arguments,
attempt to load the filename specified using any available image decoder.
This will allow you to load PNG, GIF, JPEG, BMP and DDS files,
and possibly other files as well, depending on your operating system
and additional installed modules (see the next section for details).
If the image cannot be loaded, an
ImageDecodeException will be raised.
You can load an image from any file-like object providing a read method by specifying the file keyword parameter:
kitten_stream = open('kitten.png', 'rb') kitten = pyglet.image.load('kitten.png', file=kitten_stream)
In this case the filename
kitten.png is optional, but gives a hint to
the decoder as to the file type (it is otherwise unused when a file object
Image drawing is usually done in the window’s
on_draw() event handler.
It is possible to draw individual images directly, but usually you will
want to create a “sprite” for each appearance of the image on-screen.
A Sprite is a full featured class for displaying instances of Images or Animations in the window. Image and Animation instances are mainly concerned with the image data (size, pixels, etc.), wheras Sprites also include additional properties. These include x/y location, scale, rotation, opacity, color tint, visibility, and both horizontal and vertical scaling. Multiple sprites can share the same image; for example, hundreds of bullet sprites might share the same bullet image.
A Sprite is constructed given an image or animation, and can be directly
drawn with the
sprite = pyglet.sprite.Sprite(img=image) @window.event def on_draw(): window.clear() sprite.draw()
If created with an animation, sprites automatically handle displaying the most up-to-date frame of the animation. The following example uses a scheduled function to gradually move the Sprite across the screen:
def update(dt): # Move 10 pixels per second sprite.x += dt * 10 # Call update 60 times a second pyglet.clock.schedule_interval(update, 1/60.)
batch = pyglet.graphics.Batch() sprites = [pyglet.sprite.Sprite(image, batch=batch), pyglet.sprite.Sprite(image, batch=batch), # ... ] @window.event def on_draw(): window.clear() batch.draw()
When sprites are collected into a batch, no guarantee is made about the order
in which they will be drawn. If you need to ensure some sprites are drawn
before others (for example, landscape tiles might be drawn before character
sprites, which might be drawn before some particle effect sprites), use two
OrderedGroup objects to specify the
batch = pyglet.graphics.Batch() background = pyglet.graphics.OrderedGroup(0) foreground = pyglet.graphics.OrderedGroup(1) sprites = [pyglet.sprite.Sprite(image, batch=batch, group=background), pyglet.sprite.Sprite(image, batch=batch, group=background), pyglet.sprite.Sprite(image, batch=batch, group=foreground), pyglet.sprite.Sprite(image, batch=batch, group=foreground), # ...] @window.event def on_draw(): window.clear() batch.draw()
For best performance, you should use as few batches and groups as required. (See the Graphics section for more details on batch and group rendering). This will reduce the number of internal and OpenGL operations for drawing each frame.
In addition, try to combine your images into as few textures as possible;
for example, by loading images with
(see Application resources) or with Texture bins and atlases).
A common pitfall is to use the
pyglet.image.load() method to load
a large number of images. This will cause a seperate texture to be created
for each image loaded, resulting in a lot of OpenGL texture binding overhead
for each frame.
Simple image blitting¶
Drawing images directly is less efficient, but may be adequate for
simple cases. Images can be drawn into a window with the
@window.event def on_draw(): window.clear() image.blit(x, y)
The x and y coordinates locate where to draw the anchor point of the
image. For example, to center the image at
kitten.anchor_x = kitten.width // 2 kitten.anchor_y = kitten.height // 2 kitten.blit(x, y)
You can also specify an optional z component to the
This has no effect unless you have changed the default projection
or enabled depth testing. In the following example, the second
image is drawn behind the first, even though it is drawn after it:
from pyglet.gl import * glEnable(GL_DEPTH_TEST) kitten.blit(x, y, 0) kitten.blit(x, y, -0.5)
The default pyglet projection has a depth range of (-1, 1) – images drawn with a z value outside this range will not be visible, regardless of whether depth testing is enabled or not.
Images with an alpha channel can be blended with the existing framebuffer. To do this you need to supply OpenGL with a blend equation. The following code fragment implements the most common form of alpha blending, however other techniques are also possible:
from pyglet.gl import * glEnable(GL_BLEND) glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
You would only need to call the code above once during your program, before you draw any images (this is not necessary when using only sprites).
Supported image decoders¶
The following table shows which codecs are available in pyglet.
Module Class Description
Reads Microsoft DirectDraw Surface files containing compressed textures
Uses Windows Imaging Component services to decode images.
Uses Windows GDI+ services to decode images.
Uses the GTK-2.0 GDK functions to decode images.
Wrapper interface around PIL Image class.
Uses Mac OS X QuickTime to decode images.
PNG decoder written in pure Python.
BMP decoder written in pure Python.
Each of these classes registers itself with
the filename extensions it supports. The
function will try each image decoder with a matching file extension first,
before attempting the other decoders. Only if every image decoder fails
to load an image will
be raised (the origin of the exception will be the first decoder that
You can override this behaviour and specify a particular decoding instance to use. For example, in the following example the pure Python PNG decoder is always used rather than the operating system’s decoder:
from pyglet.image.codecs.png import PNGImageDecoder kitten = pyglet.image.load('kitten.png', decoder=PNGImageDecoder())
This use is not recommended unless your application has to work around specific deficiences in an operating system decoder.
Supported image formats¶
The following table lists the image formats that can be loaded on each operating system. If Pillow is installed, any additional formats it supports can also be read. See the Pillow docs for a list of such formats.
Extension Description Windows Mac OS X Linux 
Windows Bitmap X X X
Microsoft DirectDraw Surface  X X X
Graphics Interchange Format X X X
JPEG/JIFF Image X X X
JPEG 2000 X
PC Paintbrush Bitmap Graphic X
Portable Network Graphic X X X
PBM Portable Any Map Graphic Bitmap X
Sun raster graphic X
Truevision Targa Graphic X
Tagged Image File Format X X X
X11 bitmap X X
X11 icon X X
The only supported save format is PNG, unless PIL is installed, in which case any format it supports can be written.
|||Requires GTK 2.0 or later.|
|||Only S3TC compressed surfaces are supported. Depth, volume and cube textures are not supported.|
Working with images¶
- The width of the image, in pixels.
- The height of the image, in pixels.
- Distance of the anchor point from the left edge of the image, in pixels
- Distance of the anchor point from the bottom edge of the image, in pixels
The anchor point defaults to (0, 0), though some image formats may contain an intrinsic anchor point. The anchor point is used to align the image to a point in space when drawing it.
You may only want to use a portion of the complete image. You can use the
get_region() method to return an image
of a rectangular region of a source image:
image_part = kitten.get_region(x=10, y=10, width=100, height=100)
This returns an image with dimensions 100x100. The region extracted from kitten is aligned such that the bottom-left corner of the rectangle is 10 pixels from the left and 10 pixels from the bottom of the image.
Image regions can be used as if they were complete images. Note that changes to an image region may or may not be reflected on the source image, and changes to the source image may or may not be reflected on any region images. You should not assume either behaviour.
The AbstractImage hierarchy¶
The following sections deal with the various concrete image classes. All
AbstractImage, which provides
the basic interface described in previous sections.
An image of any class can be converted into a
ImageData using the
get_image_data() methods defined on
AbstractImage. For example, to load an image
and work with it as an OpenGL texture:
kitten = pyglet.image.load('kitten.png').get_texture()
There is no penalty for accessing one of these methods if object is already of the requested class. The following table shows how concrete classes are converted into other classes:
glGetTexImage2D, crop resulting image.
You should try to avoid conversions which use
glReadPixels, as these can impose a substantial performance penalty by
transferring data in the “wrong” direction of the video bus, especially on
|||(1, 2) |
|||If the required texture compression extension is not present, the
image is decompressed in memory and then supplied to OpenGL via
|||It is not currently possible to retrieve |
Accessing or providing pixel data¶
ImageData class represents an image as a string
or sequence of pixel data, or as a ctypes pointer. Details such as the pitch
and component layout are also stored in the class. You can access an
ImageData object for any image with
kitten = pyglet.image.load('kitten.png').get_image_data()
The design of
ImageData is to allow applications
to access the detail in the format they prefer, rather than having to
understand the many formats that each operating system and OpenGL make use of.
The pitch and format properties determine how the bytes are arranged. pitch gives the number of bytes between each consecutive row. The data is assumed to run from left-to-right, bottom-to-top, unless pitch is negative, in which case it runs from left-to-right, top-to-bottom. There is no need for rows to be tightly packed; larger pitch values are often used to align each row to machine word boundaries.
The format property gives the number and order of color components. It is a string of one or more of the letters corresponding to the components in the following table:
R Red G Green B Blue A Alpha L Luminance I Intensity
For example, a format string of
"RGBA" corresponds to four bytes of
colour data, in the order red, green, blue, alpha. Note that machine
endianness has no impact on the interpretation of a format string.
The length of a format string always gives the number of bytes per pixel. So,
the minimum absolute pitch for a given image is
To retrieve pixel data in a particular format, use the get_data method,
specifying the desired format and pitch. The following example reads tightly
packed rows in
RGB format (the alpha component, if any, will be
kitten = kitten.get_image_data() data = kitten.get_data('RGB', kitten.width * 3)
data always returns a string, however pixel data can be set from a ctypes array, stdlib array, list of byte data, string, or ctypes pointer. To set the image data use set_data, again specifying the format and pitch:
kitten.set_data('RGB', kitten.width * 3, data)
You can also create
ImageData directly, by providing
each of these attributes to the constructor. This is any easy way to load
textures into OpenGL from other programs or libraries.
pyglet can use several methods to transform pixel data from one format to another. It will always try to select the most efficient means. For example, when providing texture data to OpenGL, the following possibilities are examined in order:
- Can the data be provided directly using a built-in OpenGL pixel format such
- Is there an extension present that handles this pixel format?
- Can the data be transformed with a single regular expression?
- If none of the above are possible, the image will be split into separate scanlines and a regular expression replacement done on each; then the lines will be joined together again.
The following table shows which image formats can be used directly with steps 1 and 2 above, as long as the image rows are tightly packed (that is, the pitch is equal to the width times the number of components).
Format Required extensions
If the image data is not in one of these formats, a regular expression will be constructed to pull it into one. If the rows are not tightly packed, or if the image is ordered from top-to-bottom, the rows will be split before the regular expression is applied. Each of these may incur a performance penalty – you should avoid such formats for real-time texture updates if possible.
Image sequences and atlases¶
Sometimes a single image is used to hold several images. For example, a “sprite sheet” is an image that contains each animation frame required for a character sprite animation.
pyglet provides convenience classes for extracting the individual images from such a composite image as if it were a simple Python sequence. Discrete images can also be packed into one or more larger textures with texture bins and atlases.
An “image grid” is a single image which is divided into several smaller images by drawing an imaginary grid over it. The following image shows an image used for the explosion animation in the Astraea example.
This image has one row and eight columns. This is all the information you
need to create an
explosion = pyglet.image.load('explosion.png') explosion_seq = pyglet.image.ImageGrid(explosion, 1, 8)
The images within the grid can now be accessed as if they were their own images:
frame_1 = explosion_seq frame_2 = explosion_seq
Images with more than one row can be accessed either as a single-dimensional sequence, or as a (row, column) tuple; as shown in the following diagram.
Image sequences can be sliced like any other sequence in Python. For example, the following obtains the first four frames in the animation:
start_frames = explosion_seq[:4]
explosion_tex_seq = image.TextureGrid(explosion_seq)
TextureGrid is extremely efficient for drawing many
sprites from a single texture. One problem you may encounter, however,
is bleeding between adjacent images.
When OpenGL renders a texture to the screen, by default it obtains each pixel
colour by interpolating nearby texels. You can disable this behaviour by
switching to the
GL_NEAREST interpolation mode, however you then lose the
benefits of smooth scaling, distortion, rotation and sub-pixel positioning.
You can alleviate the problem by always leaving a 1-pixel clear border around each image frame. This will not solve the problem if you are using mipmapping, however. At this stage you will need a 3D texture.
You can create a 3D texture from any sequence of images, or from an
ImageGrid. The images must all be of the same
dimension, however they need not be powers of two (pyglet takes care of
this by returning
as with a regular
In the following example, the explosion texture from above is uploaded into a 3D texture:
explosion_3d = pyglet.image.Texture3D.create_for_image_grid(explosion_seq)
You could also have stored each image as a separate file and used
pyglet.image.Texture3D.create_for_images() to create the 3D texture.
Once created, a 3D texture behaves like any other
AbstractImageSequence; slices return
TextureRegion for an image plane within the texture.
TextureGrid, though, you cannot blit a
Texture3D in its entirety.
Texture bins and atlases¶
Image grids are useful when the artist has good tools to construct the larger images of the appropriate format, and the contained images all have the same size. However it is often simpler to keep individual images as separate files on disk, and only combine them into larger textures at runtime for efficiency.
TextureAtlas is initially an empty texture,
but images of any size can be added to it at any time. The atlas takes care
of tracking the “free” areas within the texture, and of placing images at
appropriate locations within the texture to avoid overlap.
It’s possible for a
TextureAtlas to run out
of space for new images, so applications will need to either know the correct
size of the texture to allocate initally, or maintain multiple atlases as
each one fills up.
TextureBin class provides a simple means
to manage multiple atlases. The following example loads a list of images,
then inserts those images into a texture bin. The resulting list is a list of
TextureRegion images that map
into the larger shared texture atlases:
images = [ pyglet.image.load('img1.png'), pyglet.image.load('img2.png'), # ... ] bin = pyglet.image.atlas.TextureBin() images = [bin.add(image) for image in images]
pyglet.resource module (see Application resources) uses
texture bins internally to efficiently pack images automatically.
While image sequences and atlases provide storage for related images, they alone are not enough to describe a complete animation.
Animation class manages a list of
AnimationFrame objects, each of
which references an image and a duration (in seconds). The storage of
the images is up to the application developer: they can each be discrete, or
packed into a texture atlas, or any other technique.
An animation can be loaded directly from a GIF 89a image file with
load_animation() (supported on Linux, Mac OS X
and Windows) or constructed manually from a list of images or an image
sequence using the class methods (in which case the timing information
will also need to be provided).
add_to_texture_bin() method provides
a convenient way to pack the image frames into a texture bin for efficient
Individual frames can be accessed by the application for use with any kind of
rendering, or the entire animation can be used directly with a
Sprite (see next section).
The following example loads a GIF animation and packs the images in that animation into a texture bin. A sprite is used to display the animation in the window:
animation = pyglet.image.load_animation('animation.gif') bin = pyglet.image.atlas.TextureBin() animation.add_to_texture_bin(bin) sprite = pyglet.sprite.Sprite(img=animation) window = pyglet.window.Window() @window.event def on_draw(): window.clear() sprite.draw() pyglet.app.run()
When animations are loaded with
Application resources) the frames are automatically packed into a texture bin.
This example program is located in examples/programming_guide/animation.py, along with a sample GIF animation file.
pyglet provides a basic representation of the framebuffer as components of the
AbstractImage hierarchy. At this stage this
representation is based off OpenGL 1.1, and there is no support for newer
features such as framebuffer objects. Of course, this doesn’t prevent you
using framebuffer objects in your programs –
this functionality – just that they are not represented as
A framebuffer consists of
- One or more colour buffers, represented by
- An optional depth buffer, represented by
- An optional stencil buffer, with each bit represented by
- Any number of auxiliary buffers, also represented by
buffers = image.get_buffer_manager()
Only the back-left color buffer can be obtained (i.e., the front buffer is inaccessible, and stereo contexts are not supported by the buffer manager):
color_buffer = buffers.get_color_buffer()
This buffer can be treated like any other image. For example, you could copy
it to a texture, obtain its pixel data, save it to a file, and so on. Using
texture attribute is particularly
useful, as it allows you to perform multipass rendering effects without
needing a render-to-texture extension.
The depth buffer can be obtained similarly:
depth_buffer = buffers.get_depth_buffer()
When a depth buffer is converted to a texture, the class used will be a
DepthTexture, suitable for use with shadow map
The auxiliary buffers and stencil bits are obtained by requesting one, which will then be marked as “in-use”. This permits multiple libraries and your application to work together without clashes in stencil bits or auxiliary buffer names. For example, to obtain a free stencil bit:
mask = buffers.get_buffer_mask()
The buffer manager maintains a weak reference to the buffer mask, so that when you release all references to it, it will be returned to the pool of available masks.
Similarly, a free auxiliary buffer is obtained:
aux_buffer = buffers.get_aux_buffer()
When using the stencil or auxiliary buffers, make sure you explicitly request these when creating the window. See OpenGL configuration options for details.
This section assumes you are familiar with texture mapping in OpenGL (for example, chapter 9 of the OpenGL Programming Guide).
kitten = image.load('kitten.jpg') texture = kitten.get_texture()
Textures are automatically created and used by
ImageData when blitted. Itis useful to use
textures directly when aiming for high performance or 3D applications.
Texture class represents any texture object.
target attribute gives the
texture target (for example,
id the texturename.
For example, to bind a texture:
Implementations of OpenGL prior to 2.0 require textures to have dimensions
that are powers of two (i.e., 1, 2, 4, 8, 16, …). Because of this
restriction, pyglet will always create textures of these dimensions (there are
several non-conformant post-2.0 implementations). This could have unexpected
results for a user blitting a texture loaded from a file of non-standard
dimensions. To remedy this, pyglet returns a
TextureRegion of the larger
texture corresponding to just the part of the texture covered by the original
TextureRegion has an owner attribute that
references the larger texture. The following session demonstrates this:
>>> rgba = image.load('tests/image/rgba.png') >>> rgba <ImageData 235x257> # The image is 235x257 >>> rgba.get_texture() <TextureRegion 235x257> # The returned texture is a region >>> rgba.get_texture().owner <Texture 256x512> # The owning texture has power-2 dimensions >>>
TextureRegion defines a
tex_coords attribute that gives
the texture coordinates to use for a quad mapping the whole image.
tex_coords is a 4-tuple of 3-tuple
of floats; i.e., each texture coordinate is given in 3 dimensions.
The following code can be used to render a quad for a texture region:
texture = kitten.get_texture() t = texture.tex_coords w, h = texture.width, texture.height array = (GLfloat * 32)( t, t, t, 1., x, y, z, 1., t, t, t, 1., x + w, y, z, 1., t, t, t, 1., x + w, y + h, z, 1., t, t, t, 1., x, y + h, z, 1.) glPushClientAttrib(GL_CLIENT_VERTEX_ARRAY_BIT) glInterleavedArrays(GL_T4F_V4F, 0, array) glDrawArrays(GL_QUADS, 0, 4) glPopClientAttrib()
blit() method does this.
pyglet.image.Texture.create() method to create
either a texture region from a larger power-2 sized texture,
or a texture with the exact dimensions using the
Texture internal format¶
pyglet automatically selects an internal format for the texture based on the source image’s format attribute. The following table describes how it is selected.
Format Internal format Any format with 3 components
Any format with 2 components
Any other format
Note that this table does not imply any mapping between format components and
their OpenGL counterparts. For example, an image with format
"RG" will use
GL_LUMINANCE_ALPHA as its internal format; the luminance channel will be
averaged from the red and green components, and the alpha channel will be
pyglet.image.Texture.create() class method to create a texture
with a specific internal format.
By default, all textures are created with smooth (
In some cases you may wish to have different filtered applied. Retro style
pixel art games, for example, would require sharper textures. To achieve this,
GL_NEAREST to the min_filter and mag_filter parameters when
creating a texture. It is also possible to set the default filtering by
setting the default_min_filter and default_mag_filter class attributes
on the Texture class. This will cause all textures created internally by
pyglet to use these values:
pyglet.image.Texture.default_min_filter = GL_LINEAR pyglet.image.Texture.default_mag_filter = GL_LINEAR
Saving an image¶
Any image can be saved using the save method:
or, specifying a file-like object:
kitten_stream = open('kitten.png', 'wb') kitten.save('kitten.png', file=kitten_stream)
The following example shows how to grab a screenshot of your application window:
Note that images can only be saved in the PNG format unless the Pillow library is installed.