1、一般证件照的尺寸有小一寸、一寸、小二寸、二寸、五寸、六寸、七寸（横向）以及身份证照片的大小，用python获取各种尺寸的证件照
2、根据查找的资料，每种尺寸对应的像素大小如下表：
| 图片 |
像素大小 |
| 小一寸 |
260x390 |
| 一寸 |
295x413 |
| 小二寸 |
390x567 |
| 二寸
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|
413x636 |
| 5寸 |
840x1200 |
| 6寸 |
960x1440 |
| 7寸 |
1680x1200 |
| 身份证大头照 |
358x441 |
3、图片裁剪
一般而言，修改图片大小用opencv直接resize就ok了，但是问题是resize到特定大小会使照片产生形变，所以必须先对图片进行裁剪。图片要怎么裁剪？裁剪多大？
方法：
（1）计算标准图片的宽高比例ratio1，计算原图的宽高比例ratio2，ratio = w/h
（2）ratio2 >= ratio1，进行左右裁剪，使w变小达到标准ratio1的比例
（3）ratio2 < ratio1，进行下裁剪，使h变小达到标准ratio1的比例（不进行上裁剪就是怕人头被剪到）
（4）resize到标准的尺寸
4、代码
import cv2
class ImageSize:
def __init__(self):
# 小一寸
self._lt_one_inch_w = 260
self._lt_one_inch_h = 390
self._lt_one_ratio= self._lt_one_inch_w / self._lt_one_inch_h
# 一寸
self._one_inch_w = 295
self._one_inch_h = 413
self._one_ratio= self._one_inch_w / self._one_inch_h
# 小二寸
self._lt_two_inch_w = 390
self._lt_two_inch_h = 567
self._lt_two_ratio= self._lt_two_inch_w / self._lt_two_inch_h
# 二寸
self._two_inch_w = 413
self._two_inch_h = 636
self._two_ratio= self._two_inch_w / self._two_inch_h
# 五寸
self._five_inch_w = 840
self._five_inch_h = 1200
self._five_ratio= self._five_inch_w / self._five_inch_h
# 六寸
self._six_inch_w = 960
self._six_inch_h = 1440
self._six_ratio= self._six_inch_w / self._six_inch_h
# 七寸
self._seven_inch_w = 1680
self._seven_inch_h = 1200
self._seven_ratio= self._seven_inch_w / self._seven_inch_h
# ID card
self._id_inch_w = 358
self._id_inch_h = 441
self._id_ratio= self._id_inch_w / self._id_inch_h
def lt_one_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._lt_one_ratio:
ratio_img = self.crop_l_r(img, self._lt_one_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._lt_one_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._lt_one_inch_w, self._lt_one_inch_h))
return resize_img
def one_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._one_ratio:
ratio_img = self.crop_l_r(img, self._one_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._one_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._one_inch_w, self._one_inch_h))
return resize_img
def lt_two_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._lt_two_ratio:
ratio_img = self.crop_l_r(img, self._lt_two_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._lt_two_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._lt_two_inch_w, self._lt_two_inch_h))
return resize_img
def two_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._two_ratio:
ratio_img = self.crop_l_r(img, self._two_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._two_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._two_inch_w, self._two_inch_h))
return resize_img
def five_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._five_ratio:
ratio_img = self.crop_l_r(img, self._five_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._five_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._five_inch_w, self._five_inch_h))
return resize_img
def six_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._six_ratio:
ratio_img = self.crop_l_r(img, self._six_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._six_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._six_inch_w, self._six_inch_h))
return resize_img
def seven_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._seven_ratio:
ratio_img = self.crop_l_r(img, self._seven_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._seven_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._seven_inch_w, self._seven_inch_h))
return resize_img
def id_inch(self, img):
img = img
h, w = img.shape[:2]
img_ratio = w / h
if img_ratio >= self._id_ratio:
ratio_img = self.crop_l_r(img, self._id_ratio, h, w)
else:
ratio_img = self.crop_d(img, self._id_ratio, h, w)
resize_img = cv2.resize(ratio_img, (self._id_inch_w, self._id_inch_h))
return resize_img
def crop_l_r(self, img, ratio, h, w):
"""
左右裁剪
图片大小比例 > ratio
"""
crop_w = int(ratio * h)
# 将w左右裁剪成这个crop_w的大小
hide_w = (w - crop_w) // 2
return_img = img[:, hide_w:w - hide_w]
return return_img
def crop_d(self, img, ratio, h, w):
"""
图片下裁剪
图片的大小比例 < ratio
"""
crop_h = int(w / ratio)
hide_h = h - crop_h
return_img = img[:h-hide_h, :]
return return_img
if __name__ == "__main__":
image_path = "1.jpg"
img = cv2.imread(image_path)
imagesize = ImageSize()
resize_img = imagesize.lt_one_inch(img)
cv2.imwrite('resize.jpg', resize_img)