Python枕头：为透明度制作渐变

我有在图像上添加渐变的代码

def st(path, gradient_magnitude=2.):
    im = Image.open(path)
    if im.mode != 'RGBA':
        im = im.convert('RGBA')
    width, height = im.size
    gradient = Image.new('L', (width, 1), color=0xFF)
    for x in range(width):
        gradient.putpixel((x, 0), int(255 * (1 - gradient_magnitude * float(x) / width)))
    alpha = gradient.resize(im.size)
    black_im = Image.new('RGBA', (width, height), color=0x000000)
    black_im.putalpha(alpha)
    gradient_im = Image.alpha_composite(im, black_im)
    gradient_im.save('out.jpg', 'JPEG')

跑步后我得到了这张照片

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如何使渐变更透明？

试试这个。初始不透明度值为0.9或0.95应该可以满足您的需要。我还对代码进行了一点重构，因为它以前很混乱。无论是谁写了这封信，都应该被告发，并远离电脑。；-）

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使用

alpha=0.5

而不是

alpha=gradient.resize（im.size）

我得到了这个错误类型错误：需要整数参数，如果alpha–新的alpha层，它应该如何工作。这可以是与此图像大小相同的“L”或“1”图像，也可以是整数或其他颜色值。这里又是黑色的，谢谢！这是我第一次尝试图像处理，我将研究更多的文档和文章。谢谢一如既往，这是我的荣幸。你开始了解线

a=int（（初始不透明度*255。）*（1.-渐变*浮点（x）/宽度））是如何工作的了吗？这就是所有神奇之处（取消对print语句的注释可能会有所帮助）。之后，它实际上只是将alpha应用于黑色图像，然后将黑色图像与输入图像混合。
from PIL import Image

def apply_black_gradient(path_in, path_out='out.png',
                         gradient=1., initial_opacity=1.):
    """
    Applies a black gradient to the image, going from left to right.

    Arguments:
    ---------
        path_in: string
            path to image to apply gradient to
        path_out: string (default 'out.png')
            path to save result to
        gradient: float (default 1.)
            gradient of the gradient; should be non-negative;
            if gradient = 0., the image is black;
            if gradient = 1., the gradient smoothly varies over the full width;
            if gradient > 1., the gradient terminates before the end of the width;
        initial_opacity: float (default 1.)
            scales the initial opacity of the gradient (i.e. on the far left of the image);
            should be between 0. and 1.; values between 0.9-1. give good results
    """

    # get image to operate on
    input_im = Image.open(path_in)
    if input_im.mode != 'RGBA':
        input_im = input_im.convert('RGBA')
    width, height = input_im.size

    # create a gradient that
    # starts at full opacity * initial_value
    # decrements opacity by gradient * x / width
    alpha_gradient = Image.new('L', (width, 1), color=0xFF)
    for x in range(width):
        a = int((initial_opacity * 255.) * (1. - gradient * float(x)/width))
        if a > 0:
            alpha_gradient.putpixel((x, 0), a)
        else:
            alpha_gradient.putpixel((x, 0), 0)
        # print '{}, {:.2f}, {}'.format(x, float(x) / width, a)
    alpha = alpha_gradient.resize(input_im.size)

    # create black image, apply gradient
    black_im = Image.new('RGBA', (width, height), color=0) # i.e. black
    black_im.putalpha(alpha)

    # make composite with original image
    output_im = Image.alpha_composite(input_im, black_im)
    output_im.save(path_out, 'PNG')

    return