why must display be initialized when setting palette?

why must display be initialized when setting palette? - python

I want to manually create and save a color-indexed image (palette) as a PNG file, using pygame :
# create the bitmap
res = pygame.Surface((src.width, src.height), depth=8)
# create the palette
res.set_palette([pygame.Color((0, 0, 0, 0)), ...])
pygame.image.save(res, "test.png")
But I get :
error: cannot set palette without pygame.display initialized
on the set_palette line.
Of course, it isn't difficult to initialize some dummy display, but I don't see why it should be the case. Nothing is displayed, and nothing seems display dependant in my code...
Also, it's totally useless to initialize pygame or display when you manipulate 32 bits Surfaces. What's the difference between them ?

The reason is because the pygame source says so :)
But I couldn’t find any reason it was necessary, so I recently removed that check in https://github.com/pygame/pygame/pull/3259.
So this will not be the case in the next pygame release.

Your code is wrong, because you create a surface no alpha channel (no SRCALPHA flag), but set an alpha channel with 0. Set a color without alpha channel:
res.set_palette([pygame.Color((0, 0, 0, 0)), ...])
res.set_palette([pygame.Color((0, 0, 0)), ...])
A pygame.Surface is somehow associated with the display and is created in a format that best suits the display surface. You need to initialize Pygame with pygame.init() or initialize at least the display module with pygame.display.init().
Minimal working example:
import pygame
pygame.display.init()
res = pygame.Surface((1, 1), depth=8)
# create the palette
res.set_palette([pygame.Color((0, 0, 0))])

Related

No Video Mode Has Been Set Error, cannot load in images [duplicate]

I am just setting up some functions for my game but my script fails to load the image
#used variables
# x, y for alien location
# nPc for the aliens image
#
#
#
#
#
#
#
#
#
#
#set up
import pygame, sys, random, time, math
from pygame.locals import *
pygame.init()
nPc = '/home/claude/Dropbox/Bowtie/Prisim/Images/Alien_Races/Standered/alien_1.png'
nPc = pygame.image.load(nPc).convert_alpha()
def loc_alien():
x = random.randint(0, 400)
y = randaom.randint(0, 400)
def spawn_alien(x, y):
screen.blit(nPc, (x, y))
when I run this I wont nothing to happen as I am not using the functions yet, but when I do run it I get this error
Traceback (most recent call last):
File "/home/claude/Dropbox/Bowtie/Prisim/Scripts/aliens.py", line 26, in <module>
nPc = pygame.image.load(nPc).convert_alpha()
error: No video mode has been set
anyone know what I'm doing wrong?

I believe that you need to call:
screen = pygame.display.set_mode((800, 600)) # change to the real resolution
this call will actually return the surface that you want to blit on. Below is the documentation from the linked resource.
pygame.display.set_mode()
Initialize a window or screen for display
set_mode(resolution=(0,0), flags=0, depth=0) -> Surface
This function will create a display Surface. The arguments passed in
are requests for a display type. The actual created display will be
the best possible match supported by the system.
The resolution argument is a pair of numbers representing the width
and height. The flags argument is a collection of additional options.
The depth argument represents the number of bits to use for color.
The Surface that gets returned can be drawn to like a regular Surface
but changes will eventually be seen on the monitor.
If no resolution is passed or is set to (0, 0) and pygame uses SDL
version 1.2.10 or above, the created Surface will have the same size
as the current screen resolution. If only the width or height are set
to 0, the Surface will have the same width or height as the screen
resolution. Using a SDL version prior to 1.2.10 will raise an
exception.
It is usually best to not pass the depth argument. It will default to
the best and fastest color depth for the system. If your game requires
a specific color format you can control the depth with this argument.
Pygame will emulate an unavailable color depth which can be slow.
When requesting fullscreen display modes, sometimes an exact match for
the requested resolution cannot be made. In these situations pygame
will select the closest compatible match. The returned surface will
still always match the requested resolution.
The flags argument controls which type of display you want. There are
several to choose from, and you can even combine multiple types using
the bitwise or operator, (the pipe “|” character). If you pass 0 or no
flags argument it will default to a software driven window. Here are
the display flags you will want to choose from:
pygame.FULLSCREEN create a fullscreen display
pygame.DOUBLEBUF recommended for HWSURFACE or OPENGL
pygame.HWSURFACE hardware accelerated, only in FULLSCREEN
pygame.OPENGL create an OpenGL renderable display
pygame.RESIZABLE display window should be sizeable
pygame.NOFRAME display window will have no border or controls
For example:
# Open a window on the screen
screen_width=700
screen_height=400
screen=pygame.display.set_mode([screen_width,screen_height])

Do not forgot to create your surface before creating variables with images in it
like this:
win = pygame.display.set_mode((576, 1024))
background_day = pygame.image.load("background-day.png").convert()
not like this:
background_day = pygame.image.load("background-day.png").convert()
win = pygame.display.set_mode((576, 1024))

How base object controls the camera in Panda3d

I was toying around with creating custom geometry in Panda3d engine. And next code works 100% correct.
class FooBarTriangle(ShowBase):
def __init__(self):
super(self).__init__()
self.disable_mouse()
self.set_frame_rate_meter(True)
self.accept("escape", sys.exit)
self.accept("space", lambda: print(self.camera.get_pos()))
self.camera.set_pos(0, 0, 10)
self.camera.look_at(0, 0, 0)
self._add_light()
self._add_triangle()
def _add_light(self):
# Adds a point light
pass
def _add_triangle(self):
# Adds a single triangle in a certain place
pass
Mysterious things happen when I remove base.disableMouse() from my code. I expect my camera to be movable and appear in the (0, 0, 10) position, looking at (0, 0, 0). But, instead, camera is in the position (0, 0, 0) and I don't know where does it look.
Why does it happen?

This happens, because Panda3D has a default camera control in place (the default camera driver), if you don't call disableMouse(), Panda3D will not move your camera through calls to camera.set_pos(x, y, z), but only allow movement through the specified controls as can be read up here and here in the manual.
You either have to write your own camera controller if you wish to be able to place your camera anywhere other than (0, 0, 0) through code or just use the controls indicated on the links above to move around the scene.

python error, "No video mode has been set" although it is set [duplicate]

I am just setting up some functions for my game but my script fails to load the image
#used variables
# x, y for alien location
# nPc for the aliens image
#
#
#
#
#
#
#
#
#
#
#set up
import pygame, sys, random, time, math
from pygame.locals import *
pygame.init()
nPc = '/home/claude/Dropbox/Bowtie/Prisim/Images/Alien_Races/Standered/alien_1.png'
nPc = pygame.image.load(nPc).convert_alpha()
def loc_alien():
x = random.randint(0, 400)
y = randaom.randint(0, 400)
def spawn_alien(x, y):
screen.blit(nPc, (x, y))
when I run this I wont nothing to happen as I am not using the functions yet, but when I do run it I get this error
Traceback (most recent call last):
File "/home/claude/Dropbox/Bowtie/Prisim/Scripts/aliens.py", line 26, in <module>
nPc = pygame.image.load(nPc).convert_alpha()
error: No video mode has been set
anyone know what I'm doing wrong?

Do not forgot to create your surface before creating variables with images in it
like this:
win = pygame.display.set_mode((576, 1024))
background_day = pygame.image.load("background-day.png").convert()
not like this:
background_day = pygame.image.load("background-day.png").convert()
win = pygame.display.set_mode((576, 1024))

setting alpha using pixels_alpha in pygame

I'm using pygame for image editing (not displaying). (Yes, I know there are other options like PIL/pillow, but pygame should work for this.)
I want to draw and save an image where I'm individually setting the alpha values of each pixel according to a formula (I'm drawing a complicated RGBA profile). It seems that pixels_alpha is the right way to do this. But when I change pixels_alpha it's ignored, the image just stays transparent. Here's my code...
import pygame as pg
import os
def init_transparent(img_width, img_height):
"""
Create a new surface with width and height, starting with transparent
background. This part works!
"""
os.environ['SDL_VIDEODRIVER'] = 'dummy'
pg.init()
pg.display.init()
# next command enables alpha
# see http://stackoverflow.com/questions/14948711/
pg.display.set_mode((img_width, img_height), 0, 32)
# pg.SRCALPHA is a flag that turns on per-pixel alpha.
return pg.Surface((img_width, img_height), pg.SRCALPHA)
def make_semitransparent_image():
surf = init_transparent(20, 20)
# alphas should be a direct reference to the alpha data in surf
alphas = pg.surfarray.pixels_alpha(surf)
# alphas is a uint8-dtype numpy array. Right now it's all zeros.
for i in range(20):
for j in range(20):
# Since pixels_alpha gave me a uint8 array, I infer that
# alpha=255 means opaque. (Right?)
alphas[i,j] = 200
pg.image.save(surf, '/home/steve/Desktop/test.png')
make_semitransparent_image()
Again, it saves an image but the image looks completely transparent, no matter what value I set alphas to. What am I doing wrong here? (Using Python 2.7, pygame 1.9.1release.) (Thanks in advance!)

The Pygame docs say that pixels_array() locks the surface as long as the resulting array exists, and that locked surface may not be drawn correctly. It seems to be the case that they are not saved correctly, too. You need to throw away the alphas surfarray object before calling image.save(). This can be done by adding del alphas just before image.save().
(Note that this is more a workaround than a proper fix. Adding del alphas can only have a reliable effect only on CPython (and not PyPy, Jython, IronPython). Maybe you can really "close" a surfarray objects, the same way you can either close a file or merely forget about it?)

Eliminate unnecessary drawing of an image when using dc?

I have three questions that I could really use some help on. Hope I'm not asking too much.
1) I am designing a simple GUI that contains one frame and one panel. Let's say I have two images that I draw on the panel using dc. One image will be continually fade in and out (on a timer), and the second is stationary (doesn't change). The fading is accomplished by changing the opacity of the image and use dc.Clear() before redrawing the new version of the image.
My question is this: how would I draw the fading in/out image without affecting the second image which does not change? It seems like this causes unnecessary drawing as the stationary image will be redrawn alongside the fading image. Could I selectively clear just the first image without affecting the second? This is my drawing function:
def on_paint(self, event):
dc = wx.PaintDC(self)
dc = wx.BufferedDC(dc)
brush = wx.Brush('#3B3B3B')
dc.SetBackground(brush)
dc.Clear()
# Draw the first image (stationary)
dc.DrawBitmap(stationaryBitmap, 120, 0, True)
# Draw the second image (fading)
image = self.image.AdjustChannels(1, 1, 1, self.factoralpha)
fadingBitmap = wx.BitmapFromImage(image)
dc.DrawBitmap(fadingBitmap, 120, 0, True)
2) How can I bind an event to a wx.Image object? I would like to be able to click on the fading in/out image, though I can't seem to assign it an id. The goal is to bind an event similar to what I could do with a wx.StaticBitmap.
self.image = wx.Image("C:\image.png", wx.BITMAP_TYPE_PNG)
# Trying to bind an event, but no ID is assigned
self.Bind(wx.EVT_BUTTON, self.go_button, id=self.image.GetId())
3) Is it possible to place wx.DrawBitmap in a sizer? It appears that it only takes an x,y coordinate pair.
dc.DrawBitmap(bitmap, 120, 0, True)
Thanks everyone.

1) For the Performance, I would recommend using a MemoryDC and update the Drawing only it is required. See here: BufferedCanvas. You may want to use more than 2 buffers because you are using 2 images (see example).
2) I don't know about this, but have you tried to do the binding to a panel and fade the panel in/out?
You can directly paint on a wx.Panel.
Regards

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