python-3.x - 将自己的图像转换为 MNIST 的图像

Question

我是 tensorflow 的新手。
我使用 MNIST 的训练数据训练了数字预测模型。
然后我使用我自己的图像测试模型。
它无法预测实际结果。

问题是:

MNIST 的图像需要黑白

图像经过尺寸标准化以适合 20x20 像素框，并使用质心在 28x28 图像中居中。

我不想用 OpenCV

问题是 如何将我自己的手写数字图像移动到 28x28 图像的中心。自己的图像可以是任何颜色，该图像可以更改黑白 MNIST 的图像

Answer 1

from PIL import Image, ImageFilter


def imageprepare(argv):
    """
    This function returns the pixel values.
    The imput is a png file location.
    """
    im = Image.open(argv).convert('L')
    width = float(im.size[0])
    height = float(im.size[1])
    newImage = Image.new('L', (28, 28), (255))  # creates white canvas of 28x28 pixels

    if width > height:  # check which dimension is bigger
        # Width is bigger. Width becomes 20 pixels.
        nheight = int(round((20.0 / width * height), 0))  # resize height according to ratio width
        if (nheight == 0):  # rare case but minimum is 1 pixel
            nheight = 1
            # resize and sharpen
        img = im.resize((20, nheight), Image.ANTIALIAS).filter(ImageFilter.SHARPEN)
        wtop = int(round(((28 - nheight) / 2), 0))  # calculate horizontal position
        newImage.paste(img, (4, wtop))  # paste resized image on white canvas
    else:
        # Height is bigger. Heigth becomes 20 pixels.
        nwidth = int(round((20.0 / height * width), 0))  # resize width according to ratio height
        if (nwidth == 0):  # rare case but minimum is 1 pixel
            nwidth = 1
            # resize and sharpen
        img = im.resize((nwidth, 20), Image.ANTIALIAS).filter(ImageFilter.SHARPEN)
        wleft = int(round(((28 - nwidth) / 2), 0))  # caculate vertical pozition
        newImage.paste(img, (wleft, 4))  # paste resized image on white canvas

    # newImage.save("sample.png

    tv = list(newImage.getdata())  # get pixel values

    # normalize pixels to 0 and 1. 0 is pure white, 1 is pure black.
    tva = [(255 - x) * 1.0 / 255.0 for x in tv]
    print(tva)
    return tva

x=imageprepare('./image.png')#file path here
print(len(x))# mnist IMAGES are 28x28=784 pixels