如何降低枕头中线条的透明度？

Question

如何降低线条的不透明度？我想将不透明度降低到下面示例中的一行之一。

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()

我在一个示例中看到他们创建了这样的不透明度...

TRANSPARENCY = .25  # Degree of transparency, 0-100%
OPACITY = int(255 * TRANSPARENCY)

但不知道如何应用到其中一个行。有什么想法吗？

编辑

我做了一些更改（基于@Pedro Maia 的回答），它仍然不起作用，只是更改了颜色，它不会降低不透明度以查看背景颜色。

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

我必须将其转换为 RGB 才能将其导出为 'jpg'

Answer 1

使用 draw.line 可以作为参数传递 RGB 或 RGBA 只需传递透明度的值：

draw.line((100, 30, 0, 30), (0, 0, 0, int(255 * TRANSPARENCY)), 20)

同样在创建图像时将其设置为 RGBA:

img = Image.new('RGBA', (100, 100), (255, 255, 255))

Answer 2

你必须做这样的事情，这类似于的工作方式，来做你想做的（我认为）。我稍微更改了您在 EDIT 中添加到问题中的代码，以便更好地证明可以绘制不同透明度的线条。

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()

已创建 JPG 图片：

如何降低枕头中线条的透明度？

How to lower transparency to line in Pillow?

python

python-imaging-library