使用cv2.warpPerspective图像质量下降 [英] Image loses quality with cv2.warpPerspective

问题描述

我正在使用OpenCV 3.1和Python.

I am working with OpenCV 3.1 and with Python.

当我尝试用文字校正图像(校正其倾斜度)时出现问题.我正在使用cv2.warpPerspective使其成为可能，但是图像质量下降很多.您可以在此处看到图像的原始部分:

My problem comes when I try to deskew (fix the tilt of) an image with text. I am using cv2.warpPerspective to make it possible, but the image loses a lot of quality. You can see here the original part of the image:

，然后是旋转的"图像:

and then, here, the "rotated" image:

就像平滑.

我正在使用形态转换，例如:

I was using morphological transformation like:

kernel = np.ones((2, 2), np.uint8)
blur_image = cv2.erode(tresh, kernel, iterations=1)

和

white_mask2 = cv2.morphologyEx(white_mask2, cv2.MORPH_OPEN, kernel)

看看它是否可以改善某些东西，但无济于事.

to see if it improves something, but nothing.

我在SO中看到了此示例，但是那些家伙有同样的问题: 和

I saw this example here in SO, but those guys had the same problem: and

所以，我不知道该怎么办. 也许有一种不丢失图像质量的方法，或者还有另一种旋转图像而不丢失质量的方法. 我知道这种方法:

So, I don't have idea what can I do. Maybe there is a way to not losing the quality of the image, or, there's another method to rotate the image without quality lost. I know this method:

root_mat = cv2.getRotationMatrix2D(to_rotate_center, angle, 1.0)
result = cv2.warpAffine(to_rotate, root_mat, to_rotate.shape, flags=cv2.INTER_LINEAR)

但这对我不起作用，因为我必须在这里旋转每个矩形:

But it doesn't work for me, as I have to rotate every rectangle here:

，而不是整个图像.这意味着，我发现做到这一点的最佳方法是warpPerspective，它工作正常，但质量下降.我希望您能避免质量下降的建议.

and not the whole image. It means, the best way I found to do it, was warpPerspective, and it works fine, but with quality loss. I would appreciate an advice to avoid the quality lost.

推荐答案

问题与翘曲所需的插值有关.如果您不希望事情看起来更平滑，则应从默认的插值方法(c2)切换到另一种插值方法，例如INTER_NEAREST.它将帮助您提高边缘的清晰度.

The problem is related to the interpolation required by the warping. If you don't want things to appear smoother, you should switch from default interpolation method, which is INTER_LINEAR to another one, such as INTER_NEAREST. It would help you with the sharpness of the edges.

在warp调用中尝试flags=cv2.INTER_NEAREST，它是 warpPerspective( ).

Try flags=cv2.INTER_NEAREST on your warp call, be it warpAffine() or warpPerspective().

在此处中列出.... >

Interpolation flags are listed here.

enum InterpolationFlags { 
    INTER_NEAREST = 0, 
    INTER_LINEAR = 1, 
    INTER_CUBIC = 2, 
    INTER_AREA = 3, 
    INTER_LANCZOS4 = 4, 
    INTER_MAX = 7, 
    WARP_FILL_OUTLIERS = 8, 
    WARP_INVERSE_MAP = 16 
}

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