Updating part of a surface in python, or transparent surfaces

I have an application written in python that's basically an etch-a-sketch, you move pixels around with WASD and arrow keys and it leaves a trail. However, I want to add a counter for the amount of pixels on the screen. How do I have the counter update without updating the entire surface and pwning the pixel drawings?

Alternatively, can I make a surface that's completely transparent except for the text so you can see the drawing surface underneath?


Asked by: Carlos636 | Posted: 30-11-2021






Answer 1

To solve this problem, you want to have a separate surface for your Etch-a-Sketch pixels, so that they do not get clobbered when you go to refresh the screen. Unfortunately, with Rigo's scheme, the font will continue to render on top of itself, which will get messy for more than two pixel count changes.

So, here's some sample rendering code:

# Fill background
screen.fill((0xcc, 0xcc, 0xcc))
# Blit Etch-a-Sketch surface (with the drawing)
# etch_surf should be the same size as the screen
screen.blit(etch_surf, (0, 0))
# Render the pixel count
arial = pygame.font.SysFont('Arial', 20)
counter_surf = arial.render(str(pixel_count), True, (0, 0, 0))
screen.blit(counter_surf, (16, 16))
# Refresh entire screen
pygame.display.update()

Now, admittedly, updating the entire screen is rather inefficient. For this, you have two options: only refresh the screen when the drawing changes or track the location of drawing changes and refresh individual locations (see the update documentation). If you choose the second option, you will have to refresh the text and where it was previously; I would recommend having a Sprite manage this.

Answered by: Sydney975 | Posted: 01-01-2022



Answer 2

What you need is pygame.font module

#define a font surface 
spamSurface = pygame.font.SysFont('Arial', 20)

#then, in your infinite cycle...   
eggsPixels = spamSurface.render(str(pixelsOnScreen), True, (255, 255, 255))
hamDisplay.blit(eggsPixels, (10, 10))

Where spamSurface is a new font surface, eggsPixels is the value that spamSurface will render (display/show) and hamDisplay is your main surface display.

Answered by: Maddie724 | Posted: 01-01-2022



Similar questions

python - How to make a surface with a transparent background in pygame

Can someone give me some example code that creates a surface with a transparent background in pygame?


python - How to use PIL to make all white pixels transparent?

I'm trying to make all white pixels transparent using the Python Image Library. (I'm a C hacker trying to learn python so be gentle) I've got the conversion working (at least the pixel values look correct) but I can't figure out how to convert the list into a buffer to re-create the image. Here's the code img = Image.open('img.png') imga = img.convert("RGBA") datas = imga.getdata() newData = list() for i...


django - python PIL - background displayed opaque instead of transparent

I want to generate 32x32 sized thumbnails from uploaded images (actually avatars). To prevent a thumbnail from being smaller than that size, I want to create a transparent 32x32 background and paste the thumbnail on it. The code below tries to do so. However, the avatar is displayed on a black and opaque background; I lose transparency information somewhere through the process. Where am I doing wrong?...


python - Transparent FrameBuffer background in OpenGL

I want to use glClear and glClearColor to fill a frame buffer with a colour including alpha transparency. However the framebuffer always renders as opaque when binded to a texture which is rendered to the screen. I want everything which is rendered to the framebuffer to kept their transparency. I just want to change the background. See the following code: def create_texture(surface): surface...


How do I create a Status Icon / System Tray Icon with custom text and transparent background using Python and GTK?

Here is the code that I have so far to define the icon: icon_bg = gtk.gdk.pixbuf_new_from_file('gmail.png') w, h = icon_bg.get_width(), icon_bg.get_height() cmap = gtk.gdk.Colormap(gtk.gdk.visual_get_system(), False) drawable = gtk.gdk.Pixmap(None, w, h, 24) drawable.set_colormap = cmap gc = drawable.new_gc() drawable.draw_pixbuf(gc, icon_bg, 0, 0, 0, 0, w, h) drawn_icon = gtk.gdk.Pixbuf(gtk.gdk.COLORSPAC...


python - How to make cStringIO transparent to another function that expects a real local file

I came up with the following problem: CODE A works right now.. I am saving a png file called chart.png locally, and then I am loading it into the proprietary function (which I do not have access). However, in CODE B, am trying to use cStringIO.StringIO() so that I do not have to write the file "chart.png" to the disk. But I cannot find a way to pass it to the pproprietaryfunction because it is expecting a real fil...


python - PIL: How to make area transparent in PNG?

I've been using PIL to crop Images, now I also want to make certain rectangular areas transparent, say from PIL import Image im = Image.open("sample.png") transparent_area = (50,80,100,200) ...


python - Matplotlib transparent line plots

I am plotting two similar trajectories in matplotlib and I'd like to plot each of the lines with partial transparency so that the red (plotted second) doesn't obscure the blue. EDIT: Here's the image with transparent lines.


python - Transparent 3D bar graphs

I would like to generate 3D bar graphs with transparent surfaces so that I can see what is going on behind tall bars. The mplot3d API docs say that keywords are allowed for the bar3d function. I pass all the required parameters but can only output graphs with solid surfaces.


python - Partially transparent scatter plot, but with a solid color bar

In Python, with Matplotlib, how to simply do a scatter plot with transparency (alpha < 1), but with a color bar that represents their color value, but has alpha = 1? Here is what one gets, with from pylab import *; scatter(range(10), arange(0, 100, 10), c=range(10), alpha=0.2); color_bar = colorbar(): How can the color ba...






Still can't find your answer? Check out these communities...



PySlackers | Full Stack Python | NHS Python | Pythonist Cafe | Hacker Earth | Discord Python



top