Develop Reference

Keeping transparent pixels through rotozoom in pygame, Python 3

I'm currently making a game in pygame, Python 3 and a part of the code that has been giving me issues is:
for counter in range(0, 30):
particles = pygame.image.load('particles.png').convert()
particles = pygame.transform.rotozoom(particles, 36*counter, 1.1**counter).convert()
particles.set_colorkey((0, 0, 0, 0))
screen.blit(particles, particles.get_rect(centerx=480, centery=100))
pygame.display.flip()
time.sleep(0.05)
particles.png is just a few colored pixels on a transparent background. The problem is that when the image is rotated and scaled, some of those particles sort of blur out resulting in a mass of black squares around them.
How do I fix this problem? Thanks in advance!!

I've had a bad experience with pygame's rotozoom combined with transparency. Instead of loading the image and then rotozooming it, consider the following:
Using PIL library:
Convert the loaded surface to a string using pygame.image.tostring
Convert the string to an Image object
Use PIL's functions to replace rotozoom (zooming, rotating)
Convert the Image object back into a surface using the same method
Using math:
Load data about the position and color of the particles,
or infer it from the loaded surface
Use simple mathematical functions to caculate their new position,
according to the angle and zoom
Paint them using pygame.gfxdraw, pygame.draw or pygame.Surface.set_at
Good luck!

Turtle graphics window's canvas color *not* showing up in Postscript (.ps) file [duplicate]

I am new to Python and have been working with the turtle module as a way of learning the language.
Thanks to stackoverflow, I researched and learned how to copy the image into an encapsulated postscript file and it works great. There is one problem, however. The turtle module allows background color which shows on the screen but does not show in the .eps file. All other colors, i.e. pen color and turtle color, make it through but not the background color.
As a matter of interest, I do not believe the import of Tkinter is necessary since I do not believe I am using any of the Tkinter module here. I included it as a part of trying to diagnose the problem. I had also used bgcolor=Orange rather than the s.bgcolor="orange".
No Joy.
I am including a simple code example:
# Python 2.7.3 on a Mac
import turtle
from Tkinter import *
s=turtle.Screen()
s.bgcolor("orange")
bob = turtle.Turtle()
bob.circle(250)
ts=bob.getscreen()
ts.getcanvas().postscript(file = "turtle.eps")
I tried to post the images of the screen and the .eps file but stackoverflow will not allow me to do so as a new user. Some sort of spam prevention. Simple enough to visualize though, screen has background color of orange and the eps file is white.
I would appreciate any ideas.

Postscript was designed for making marks on some medium like paper or film, not raster graphics. As such it doesn't have a background color per se that can be set to given color because that would normally be the color of the paper or unexposed film being used.
In order to simulate this you need to draw a rectangle the size of the canvas and fill it with the color you want as the background. I didn't see anything in the turtle module to query the canvas object returned by getcanvas() and the only alternative I can think of is to read the turtle.cfg file if there is one, or just hardcode the default 300x400 size. You might be able to look at the source and figure out where the dimensions of the current canvas are stored and access them directly.
Update:
I was just playing around in the Python console with the turtle module and discovered that what the canvas getcanvas() returns has a private attribute called _canvas which is a <Tkinter.Canvas instance>. This object has winfo_width() and winfo_height() methods which seem to contain the dimensions of the current turtle graphics window. So I would try drawing a filled rectangle of that size and see if that gives you what you want.
Update 2:
Here's code showing how to do what I suggested. Note: The background must be drawn before any other graphics are because otherwise the solid filled background rectangle created will cover up everything else on the screen.
Also, the added draw_background() function makes an effort to save and later restore the graphics state to what it was. This may not be necessary depending on your exact usage case.
import turtle
def draw_background(a_turtle):
""" Draw a background rectangle. """
ts = a_turtle.getscreen()
canvas = ts.getcanvas()
height = ts.getcanvas()._canvas.winfo_height()
width = ts.getcanvas()._canvas.winfo_width()
turtleheading = a_turtle.heading()
turtlespeed = a_turtle.speed()
penposn = a_turtle.position()
penstate = a_turtle.pen()
a_turtle.penup()
a_turtle.speed(0) # fastest
a_turtle.goto(-width/2-2, -height/2+3)
a_turtle.fillcolor(turtle.Screen().bgcolor())
a_turtle.begin_fill()
a_turtle.setheading(0)
a_turtle.forward(width)
a_turtle.setheading(90)
a_turtle.forward(height)
a_turtle.setheading(180)
a_turtle.forward(width)
a_turtle.setheading(270)
a_turtle.forward(height)
a_turtle.end_fill()
a_turtle.penup()
a_turtle.setposition(*penposn)
a_turtle.pen(penstate)
a_turtle.setheading(turtleheading)
a_turtle.speed(turtlespeed)
s = turtle.Screen()
s.bgcolor("orange")
bob = turtle.Turtle()
draw_background(bob)
ts = bob.getscreen()
canvas = ts.getcanvas()
bob.circle(250)
canvas.postscript(file="turtle.eps")
s.exitonclick() # optional
And here's the actual output produced (rendered onscreen via Photoshop):

I haven't found a way to get the canvas background colour on the generated (Encapsulated) PostScript file (I suspect it isn't possible). You can however fill your circle with a colour, and then use Canvas.postscript(colormode='color') as suggested by #mgilson:
import turtle
bob = turtle.Turtle()
bob.fillcolor('orange')
bob.begin_fill()
bob.circle(250)
bob.begin_fill()
ts = bob.getscreen()
ts.getcanvas().postscript(file='turtle.eps', colormode='color')

Improving #martineau's code after a decade
import turtle as t
Screen=t.Screen()
Canvas=Screen.getcanvas()
Width, Height = Canvas.winfo_width(), Canvas.winfo_height()
HalfWidth, HalfHeight = Width//2, Height//2
Background = t.Turtle()
Background.ht()
Background.speed(0)
def BackgroundColour(Colour:str="white"):
Background.clear() # Prevents accumulation of layers
Background.penup()
Background.goto(-HalfWidth,-HalfHeight)
Background.color(Colour)
Background.begin_fill()
Background.goto(HalfWidth,-HalfHeight)
Background.goto(HalfWidth,HalfHeight)
Background.goto(-HalfWidth,HalfHeight)
Background.goto(-HalfWidth,-HalfHeight)
Background.end_fill()
Background.penup()
Background.home()
BackgroundColour("orange")
Bob=t.Turtle()
Bob.circle(250)
Canvas.postscript(file="turtle.eps")
This depends on what a person is trying to accomplish but generally, having the option to select which turtle to use to draw your background to me is unnecessary and can overcomplicate things so what one can do instead is have one specific turtle (which I named Background) to just update the background when desired.
Plus, rather than directing the turtle object via magnitude and direction with setheading() and forward(), its cleaner (and maybe faster) to simply give the direct coordinates of where the turtle should go.
Also for any newcomers: Keeping all of the constants like Canvas, Width, and Height outside the BackgroundColour() function speeds up your code since your computer doesn't have to recalculate or refetch any values every time the function is called.

Pyglet: blit_into texture and alpha

I've been using pyglet for a while now and I really like it. I've got one thing I'd like to do but have been unable to do so far, however.
I'm working on a 2D roleplaying game and I'd like the characters to be able to look different - that is to say, I wouldn't like use completely prebuilt sprites, but instead I'd like there to be a range of, say, hairstyles and equipment, visible on characters in the game.
So to get this thing working, I thought the most sensible way to go on about it would be to create a texture with pyglet.image.Texture.create() and blit the correct sprite source images on that texture using Texture.blit_into. For example, I could blit a naked human image on the texture, then blit a hair texture on that, etc.
human_base = pyglet.image.load('x/human_base.png').get_image_data()
hair_style = pyglet.image.load('x/human_hair1.png').get_image_data()
texture = pyglet.image.Texture.create(width=human_base.width,height=human_base.height)
texture.blit_into(human_base, x=0, y=0, z=0)
texture.blit_into(hair_style, x=0, y=0, z=1)
sprite = pyglet.sprite.Sprite(img=texture, x=0, y=0, batch=my_sprite_batch)
The problem is that blitting the second image into the texture "overwrites" the texture already blitted in. Even though both of the images have an alpha channel, the image below (human_base) is not visible after hair_style is blit on top of it.
One reading this may be wondering why do it this way instead of, say, creating two different pyglet.sprite.Sprite objects, one for human_base and one for hair_style and just move them together. One thing is the draw ordering: the game is tile-based and isometric, so sorting a visible object consisting of multiple sprites with differing layers (or ordered groups, as pyglet calls them) would be a major pain.
So my question is, is there a way to retain alpha when using blit_into with pyglet. If there is no way to do it, please, any suggestions for alternative ways to go on about this would be very much appreciated!

setting the blend function correctly should fix this:
pyglet.gl.glBlendFunc(pyglet.gl.GL_SRC_ALPHA,pyglet.gl.GL_ONE_MINUS_SRC_ALPHA)

I ran into the very same problem and couldn't find a proper solution. Apparently blitting two RGBA images/textures overlapping together will remove the image beneath. Another approache I came up with was using every 'clothing image' on every character as an independent sprite attached to batches and groups, but that was far from the optimal and reduced the FPS dramatically.
I got my own solution by using PIL
import pyglet
from PIL import Image
class main(pyglet.window.Window):
def __init__ (self):
TILESIZE = 32
super(main, self).__init__(800, 600, fullscreen = False)
img1 = Image.open('under.png')
img2 = Image.open('over.png')
img1.paste(img2,(0,0),img2.convert('RGBA'))
img = img1.transpose(Image.FLIP_TOP_BOTTOM)
raw_image=img.tostring()
self.image=pyglet.image.ImageData(TILESIZE,TILESIZE,'RGBA',raw_image)
def run(self):
while not self.has_exit:
self.dispatch_events()
self.clear()
self.image.blit(0,0)
self.flip()
x = main()
x.run()
This may well not be the optimal solution, but if you do the loading in scene loading, then it won't matter, and with the result you can do almost almost anything you want to (as long as you don't blit it on another texture, heh). If you want to get just 1 tile (or a column or a row or a rectangular box) out of a tileset with PIL, you can use the crop function.

Semi-transparent 2d VTK text background

Simple question, but I've tried a few things and nothing seems to work.
I want to overlay some statistics onto a 3d VTK scene, using 2D vtkTextActors. This works fine, but the text is at times difficult to see, depending on what appears behind it in the 3D scene.
For this reason, I'd like to add a 2d, semi-transparent "box" behind my text actors to provide a darker background.
Which VTK object is appropriate for this? I've tried so far:
vtkLegendBoxActor: Not what I want, but I can use this with no text to display a semi-transparent box on screen. I cannot size it directly and I get warnings about not initialising some of the content.
vtkImageData: Tried manually creating image data and adding it to the scene; I believe it was placed within the 3d scene and not used as an overlay. If that's not the case then I couldn't get it to show at all.
vtkCornerAnnotation: Scales with window size, is fixed to a corner and the background opacity cannot be set AFAIK.
vtkTextActor: Cannot set a background color or opacity
Can anyone tell me how they might achieve what I'm after in VTK?

I've found a way to do this with vtkPolyMapper2D which seems to work okay. It seems to be a very stupid way to do this. If there is something more elegant, I'm all ears.
import vtk
extents = [[0,0],[620,0],[620,220],[0,220]]
polyPoints = vtk.vtkPoints()
for x, y in extents:
polyPoints.InsertNextPoint(x, y, 0)
num_corners = len(extents)
polyCells = vtk.vtkCellArray()
polyCells.InsertNextCell(num_corners + 1)
for i in range(0, num_corners):
polyCells.InsertCellPoint(i)
polyCells.InsertCellPoint(0) ## Rejoin at the end
poly_profile = vtk.vtkPolyData()
poly_profile.SetPoints(polyPoints)
poly_profile.SetPolys(polyCells) ## Goes solid
cut_triangles = vtk.vtkTriangleFilter()
cut_triangles.SetInput(poly_profile)
_poly_mapper = vtk.vtkPolyDataMapper2D()
_poly_mapper.SetInput(poly_profile)
_poly_mapper.SetInputConnection(cut_triangles.GetOutputPort())
_actor = vtk.vtkActor2D()
_actor.SetMapper(_poly_mapper)
_actor.GetProperty().SetColor([0.1,0.1,0.1])
_actor.GetProperty().SetOpacity(0.5)
#Add to renderer as normal

just use vtktexture, vtkimagedata & add your own image as texture background to the vtkrenderer by reducing the opacity like a watermark. thats it

Any way to speed up Python and Pygame?

I am writing a simple top down rpg in Pygame, and I have found that it is quite slow.... Although I am not expecting python or pygame to match the FPS of games made with compiled languages like C/C++ or event Byte Compiled ones like Java, But still the current FPS of pygame is like 15. I tried rendering 16-color Bitmaps instead of PNGs or 24 Bitmaps, which slightly boosted the speed, then in desperation , I switched everything to black and white monochrome bitmaps and that made the FPS go to 35. But not more. Now according to most Game Development books I have read, for a user to be completely satisfied with game graphics, the FPS of a 2d game should at least be 40, so is there ANY way of boosting the speed of pygame?

Use Psyco, for python2:
import psyco
psyco.full()
Also, enable doublebuffering. For example:
from pygame.locals import *
flags = FULLSCREEN | DOUBLEBUF
screen = pygame.display.set_mode(resolution, flags, bpp)
You could also turn off alpha if you don't need it:
screen.set_alpha(None)
Instead of flipping the entire screen every time, keep track of the changed areas and only update those. For example, something roughly like this (main loop):
events = pygame.events.get()
for event in events:
# deal with events
pygame.event.pump()
my_sprites.do_stuff_every_loop()
rects = my_sprites.draw()
activerects = rects + oldrects
activerects = filter(bool, activerects)
pygame.display.update(activerects)
oldrects = rects[:]
for rect in rects:
screen.blit(bgimg, rect, rect)
Most (all?) drawing functions return a rect.
You can also set only some allowed events, for more speedy event handling:
pygame.event.set_allowed([QUIT, KEYDOWN, KEYUP])
Also, I would not bother with creating a buffer manually and would not use the HWACCEL flag, as I've experienced problems with it on some setups.
Using this, I've achieved reasonably good FPS and smoothness for a small 2d-platformer.

All of these are great suggestions and work well, but you should also keep in mind two things:
1) Blitting surfaces onto surfaces is faster than drawing directly. So pre-drawing fixed images onto surfaces (outside the main game loop), then blitting the surface to the main screen will be more efficient. For exmample:
# pre-draw image outside of main game loop
image_rect = get_image("filename").get_rect()
image_surface = pygame.Surface((image_rect.width, image_rect.height))
image_surface.blit(get_image("filename"), image_rect)
......
# inside main game loop - blit surface to surface (the main screen)
screen.blit(image_surface, image_rect)
2) Make sure you aren't wasting resources by drawing stuff the user can't see. for example:
if point.x >= 0 and point.x <= SCREEN_WIDTH and point.y >= 0 and point.y <= SCREEN_HEIGHT:
# then draw your item
These are some general concepts that help me keep FPS high.

When using images it is important to convert them with the convert()-function of the image.
I have read that convert() disables alpha which is normally quite slow.
I also had speed problems until I used a colour depth of 16 bit and the convert function for my images. Now my FPS are around 150 even if I blit a big image to the screen.
image = image.convert()#video system has to be initialed
Also rotations and scaling takes a lot of time to calculate. A big, transformed image can be saved in another image if it is immutable.
So the idea is to calculate once and reuse the outcome multiple times.

When loading images, if you absolutely require transparency or other alpha values, use the Surface.convert_alpha() method. I have been using it for a game I've been programming, and it has been a huge increase in performance.
E.G: In your constructor, load your images using:
self.srcimage = pygame.image.load(imagepath).convert_alpha()
As far as I can tell, any transformations you do to the image retains the performance this method calls. E.G:
self.rotatedimage = pygame.transform.rotate(self.srcimage, angle).convert_alpha()
becomes redundant if you are using an image that has had convert_alpha() ran on it.

First, always use 'convert()' because it disables alpha which makes bliting faster.
Then only update the parts of the screen that need to be updated.
global rects
rects = []
rects.append(pygame.draw.line(screen, (0, 0, 0), (20, 20), (100, 400), 1))
pygame.display.update(rects) # pygame will only update those rects
Note:
When moving a sprite you have to include in the list the rect from their last position.

You could try using Psyco (http://psyco.sourceforge.net/introduction.html). It often makes quite a bit of difference.

There are a few things to consider for a well-performing Pygame application:
Ensure that the image Surface has the same format as the display Surface. Use convert() (or convert_alpha()) to create a Surface that has the same pixel format. This improves performance when the image is blit on the display, because the formats are compatible and blit does not need to perform an implicit transformation. e.g.:
surf = pygame.image.load('my_image.png').convert_alpha()
Do not load the images in the application loop. pygame.image.load is a very time-consuming operation because the image file must be loaded from the device and the image format must be decoded. Load the images once before the application loop, but use the images in the application loop.
If you have a static game map that consists of tiles, you can buy performance by paying with memory usage. Create a large Surface with the complete map. blit the area which is currently visible on the screen:
game_map = pygame.Surface((tile_size * columns, tile_size * rows))
for x in range(columns):
for y in range(rows):
tile_image = # image for this row and column
game_map.blit(tile_image , (x * tile_size, y * tile_size))
while game:
# [...]
map_sub_rect = screen.get_rect(topleft = (camera_x, camera_y))
screen.blit(game_map, (0, 0), map_sub_rect)
# [...]
If the text is static, the text does not need to be rendered in each frame. Create the text surface once at the beginning of the program or in the constructor of a class, and blit the text surface in each frame.
If the text is dynamic, it cannot even be pre-rendered. However, the most time-consuming is to create the pygame.font.Font/pygame.font.SysFont object. At the very least, you should avoid creating the font in every frame.
In a typical application you don't need all permutations of fonts and font sizes. You just need a couple of different font objects. Create a number of fonts at the beginning of the application and use them when rendering the text. For Instance. e.g.:
fontComic40 = pygame.font.SysFont("Comic Sans MS", 40)
fontComic180 = pygame.font.SysFont("Comic Sans MS", 180)