I have a png image as background and I want to add a transparent mesh to this background but this doesn't work as expected. The background image is converted to transparent on places where I apply transparent mesh.
I am doing:
from PIL import Image, ImageDraw
map_background = Image.open(MAP_BACKGROUND_FILE).convert('RGBA')
map_mesh = Image.new('RGBA', (width, height), (0, 0, 0, 0))
draw = ImageDraw.Draw(map_mesh)
# Create mesh using: draw.line([...], fill=(255, 255, 255, 50), width=1)
...
map_background.paste(map_mesh, (0, 0), map_mesh)
But the result is:
You can see a chessboard pattern if you look carefully (used in graphics programs as no background). Transparent lines makes the background layer transparent too in places where both layers met. But I only want the transparent line to be added on top of the background.
I can solve it with:
map_background.paste((255,255,255), (0, 0), map_mesh)
but as I use different colors for different lines, I would have to make for every color this process. If I had 100 colors, then I need 100 layers what is not very good solution.
What you are trying to do is to composite the grid onto the background, and for that you need to use Image.blend or Image.composite. Here's an example using the latter to composite red lines with random alpha values onto a white background:
import Image, ImageDraw, random
background = Image.new('RGB', (100, 100), (255, 255, 255))
foreground = Image.new('RGB', (100, 100), (255, 0, 0))
mask = Image.new('L', (100, 100), 0)
draw = ImageDraw.Draw(mask)
for i in range(5, 100, 10):
draw.line((i, 0, i, 100), fill=random.randrange(256))
draw.line((0, i, 100, i), fill=random.randrange(256))
result = Image.composite(background, foreground, mask)
From left to right:
[background] [mask]
[foreground]
[result]
(If you are happy to write the result back to the background image, then you can use one of the masked versions of Image.paste, as pointed out by Paulo Scardine in a deleted answer.)
I had trouble getting the above examples to work well. Instead, this worked for me:
import numpy as np
import Image
import ImageDraw
def add_craters(image, craterization=20.0, width=256, height=256):
foreground = Image.new('RGBA', (width, height), (0, 0, 0, 0))
draw = ImageDraw.Draw(foreground)
for c in range(0, craterization):
x = np.random.randint(10, width-10)
y = np.random.randint(10, height-10)
radius = np.random.randint(2, 10)
dark_color = (0, 0, 0, 128)
draw.ellipse((x-radius, y-radius, x+radius, y+radius), fill=dark_color)
image_new = Image.composite(foreground, image, foreground)
return image_new
Related
I'm trying to make a grid, and I made a lines in one way but other way I it doesn't seem to work, I got some weird lines going in other directions. Any idea how to get it right?
from PIL import Image, ImageDraw
img = Image.new('RGB', (1000, 1000), (255, 255, 255))
draw = ImageDraw.Draw(img)
for y in range (-2000, 2000, 200):
draw.line(((y, 2000), (2000, y)), (0, 0, 0), 20)
img
Output produced by code sample
Thanks in advance!
you are trying to draw : y = -x, so:
from PIL import Image, ImageDraw
img = Image.new('RGB', (1000, 1000), (255, 255, 255))
draw = ImageDraw.Draw(img)
for x in range (-1000, 1000, 100):
draw.line(((x,-x),(x+img.size[0], -x+img.size[1])), (0, 0, 0), 20)
img.show()
I used img.size to dynamically choose the second point of the line , you can hardcode it to 2000 (x+2000,-x+2000) , If you want to keep it that way
How to lower opacity to line? I would like to lower opacity to one of line in example bellow.
from PIL import Image, ImageDraw
img = Image.new('RGB', (100, 100), (255, 255, 255))
draw = ImageDraw.Draw(img)
draw.line((100, 30, 0, 30), (0, 0, 0), 20)
draw.line((100, 70, 0, 70), (0, 0, 0), 20)
img.show()
I have seen in one example they created opacity like this...
TRANSPARENCY = .25 # Degree of transparency, 0-100%
OPACITY = int(255 * TRANSPARENCY)
But don't know how to apply to one of lines. Any ideas?
EDIT
I made some changes (based on answer of #Pedro Maia), it still doesn't work, just changes a color, it doesn't lower opacity to see background color.
from PIL import Image, ImageDraw
img = Image.new('RGBA', (500, 500), (255, 255, 255))
draw = ImageDraw.Draw(img)
TRANSPARENCY = .25 # Degree of transparency, 0-100%
draw.line((200, 0, 200, 600),(255, 0, 0), 60)
draw.line((500, 100, 0, 100), (0, 0, 0, int(255 * TRANSPARENCY)), 60)
draw.line((500, 400, 0, 400),(0, 0, 0), 60)
img
And I have to convert it to RGB to export it as 'jpg'
You would have to do something like this, which is similar to how the example code works, to do what (I think) you want to. I changed the code you added to your question in the EDIT slightly so it better demonstrates that lines of different amounts of transparency can be drawn.
from PIL import Image, ImageDraw
RED = (255, 0, 0)
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
# Calculate alpha given a 0-100% opacity value.
opacity = lambda transparency: (int(255 * (transparency/100.)),) # Returns a monuple.
def draw_transp_line(image, xy, color, width=1, joint=None):
""" Draw line with transparent color on the specified image. """
if len(color) < 4: # Missing alpha?
color += opacity(100) # Opaque since alpha wasn't specified.
# Make an overlay image the same size as the specified image, initialized to
# a fully transparent (0% opaque) version of the line color, then draw a
# semi-transparent line on it.
overlay = Image.new('RGBA', image.size, color[:3]+opacity(0))
draw = ImageDraw.Draw(overlay) # Create a context for drawing things on it.
draw.line(xy, color, width, joint)
# Alpha composite the overlay image onto the original.
image.alpha_composite(overlay)
# Create opaque white RGBA background image.
img = Image.new('RGBA', (500, 500), (255, 255, 255)+opacity(100))
draw_transp_line(img, ((200, 0), (200, 600)), RED+opacity(100), 60)
draw_transp_line(img, ((500, 100), (0, 100)), BLACK+opacity(25), 60)
draw_transp_line(img, ((150, 50), (600, 400)), BLACK+opacity(50), 60)
img = img.convert("RGB") # Remove alpha for saving in jpg format.
img.save('transparent_lines.jpg')
img.show()
JPG image created:
With draw.line you can pass as argument RGB or RGBA just pass the value of the transparency:
draw.line((100, 30, 0, 30), (0, 0, 0, int(255 * TRANSPARENCY)), 20)
Also when creating the image set it as RGBA:
img = Image.new('RGBA', (100, 100), (255, 255, 255))
I have an image with a black background. How am I supposed to draw a red shape on it? The red color should be (0,0,255) right? But it shows as black so it's not visible with a black background. The best I could do was to create a white rectangle in the following example. My question is how should I make it red? I think I'm missing something simple here. Please help.
import cv2
import numpy as np
img = np.zeros((500,500,1), np.uint16)
cv2.rectangle(img, (200, 200), (300, 300), (0, 0, 255), 5)
cv2.imshow('image',img)
cv2.waitKey(100000)
You will see the rectangle doesn't even show up:
And the best I could do was a white rectangle like this:
img = np.zeros((500,500,1), np.uint16)
cv2.rectangle(img, (200, 200), (300, 300), (2**16, 0, 0), 5)
cv2.imshow('image',img)
cv2.waitKey(100000)
You are trying to draw color (3 channels) on a black (one channel) image. You need to convert the black image to 3 channels. Here is how I do it in Python/OpenCV
import cv2
import numpy as np
# create one channel black image (grayscale)
img = np.zeros((500,500))
# convert to 3 channel black (color)
img = cv2.merge([img,img,img])
# draw on it in color
cv2.rectangle(img, (200, 200), (300, 300), (0, 0, 255), 5)
cv2.imshow('image',img)
cv2.waitKey(0)
The result is a red square outline on black background
I'm trying to create image with semitransparent shapes drawn on transparent background. For some reason instead of staying transparent, the shapes are completely covering those beneath them. My code:
from PIL import Image, ImageDraw
img = Image.new("RGBA", (256, 256), (255,0,0,127))
drawing = ImageDraw.Draw(img, "RGBA")
drawing.ellipse((127-79, 127 - 63, 127 + 47, 127 + 63), fill=(0, 255, 0, 63), outline=(0, 255, 0, 255))
drawing.ellipse((127-47, 127 - 63, 127 + 79, 127 + 63), fill=(0, 0, 255, 63), outline=(0, 0, 255, 255))
img.save("foo.png", "png")
I would expect the result to look something like (except for background not being transparent):but it looks like:
When I try to save it as GIF with img.save("foo.gif", "gif"), result is even worse. Circles are solid, no difference between outline and fill.
As I mentioned in a comment, ImageDraw.Draw doesn't do blending—whatever is drawn replaces whatever pixels that were there previously. To get the effect you want requires drawing things in a two-step process. The ellipse must first be drawn on a blank transparent background, and then that must be alpha-composited with current image (bg_img) to preserve transparency.
In the code below this has been implementing in re-usable function:
from PIL import Image, ImageDraw
def draw_transp_ellipse(img, xy, **kwargs):
""" Draws an ellipse inside the given bounding box onto given image.
Supports transparent colors
"""
transp = Image.new('RGBA', img.size, (0,0,0,0)) # Temp drawing image.
draw = ImageDraw.Draw(transp, "RGBA")
draw.ellipse(xy, **kwargs)
# Alpha composite two images together and replace first with result.
img.paste(Image.alpha_composite(img, transp))
bg_img = Image.new("RGBA", (256, 256), (255, 0, 0, 127)) # Semitransparent background.
draw_transp_ellipse(bg_img, (127-79, 127-63, 127+47, 127+63),
fill=(0, 255, 0, 63), outline=(0, 255, 0, 255))
draw_transp_ellipse(bg_img, (127-47, 127-63, 127+79, 127+63),
fill=(0, 0, 255, 63), outline=(0, 0, 255, 255))
bg_img.save("foo.png")
This is the image it created viewed in my image file editor app which renders semi-transparent portions of images with a checker-board pattern. As you can see the opaque outlines are the only part that isn't.
All 4th dimensions-transparency must be half. Also maybe problem is with drawing. Make mask for each ellipse and then sum up images. Last option- check pil function for bending images. That will propably be most certain and easiest solution.
The function for blending is:
PIL.Image. blend (im1, im2, alpha)
I am trying to make a transparent image and draw on it, and after I will addWeighted over the base image.
How can I initialize fully transparent image with width and hight in openCV python?
EDIT: I want to make a effect like in Photoshop, having stack of the layers, all stacked layers are initially transparent and drawing is performed on fully transparent layer. On the end I will merge all layers to get final image
For creating a transparent image you need a 4 channel matrix, 3 of which would represent RGB colors and the 4th channel would represent Alpha channel, To create a transparent image, you can ignore the RGB values and directly set the alpha channel to be 0. In Python OpenCV uses numpy to manipulate matrices, so a transparent image can be created as
import numpy as np
import cv2
img_height, img_width = 300, 300
n_channels = 4
transparent_img = np.zeros((img_height, img_width, n_channels), dtype=np.uint8)
# Save the image for visualization
cv2.imwrite("./transparent_img.png", transparent_img)
If you want to draw on several "layers" and then stack the drawings together, then how about this:
import cv2
import numpy as np
#create 3 separate BGRA images as our "layers"
layer1 = np.zeros((500, 500, 4))
layer2 = np.zeros((500, 500, 4))
layer3 = np.zeros((500, 500, 4))
#draw a red circle on the first "layer",
#a green rectangle on the second "layer",
#a blue line on the third "layer"
red_color = (0, 0, 255, 255)
green_color = (0, 255, 0, 255)
blue_color = (255, 0, 0, 255)
cv2.circle(layer1, (255, 255), 100, red_color, 5)
cv2.rectangle(layer2, (175, 175), (335, 335), green_color, 5)
cv2.line(layer3, (170, 170), (340, 340), blue_color, 5)
res = layer1[:] #copy the first layer into the resulting image
#copy only the pixels we were drawing on from the 2nd and 3rd layers
#(if you don't do this, the black background will also be copied)
cnd = layer2[:, :, 3] > 0
res[cnd] = layer2[cnd]
cnd = layer3[:, :, 3] > 0
res[cnd] = layer3[cnd]
cv2.imwrite("out.png", res)
To convert an image's white parts to transparent:
import cv2
import numpy as np
img = cv2.imread("image.png", cv2.IMREAD_UNCHANGED)
img[np.where(np.all(img[..., :3] == 255, -1))] = 0
cv2.imwrite("transparent.png", img)