lenna小姐姐作为图像领域中的hello world，20世纪的跨界达人，几代人的战斗对象。对于入门Python的你如果了解了lenna小姐姐，那可相当于半根脚趾头踏入了图像处理的大门，所以今天从下面几个方面给大家介绍一下lenna小姐姐
lenna是谁？
为什么选这张图？
都对lenna做了什么？
lenna近照
lenna是谁？
莱娜·瑟德贝里（瑞典文：Lena Soderberg），1951年3月31日出生于瑞典，在1972年11月期的《花花公子》杂志中，她化名为莱娜·舍布洛姆，成为了当期的玩伴女郎。
她的照片（即莱娜图）后来被数字图像处理领域所广泛使用。
为什么选这张图？
主要有三个原因
这张图适度的混合了细节、平滑区域、阴影和纹理，从而能很好的测试各种图像处理算法
这张图的Lena是个美女，对于图像处理界的研究者（大部分都是男性）来说，美女图可以有效的吸引他们来做研究
该照片的全图实在太吸引眼球，广为流传的图仅为全图的1/3，(全图这里实在放不了，一放就封号)
都对lenna做了什么？
通过cv2包，科研人员对这张图无所不用其极，绘图显示、切分、滤镜、校正、旋转、变换，行哥这里将源码和结果一一附上
1.灰度显示
img_gray = cv2.imread('lenna.jpg',0) cv2.imshow('lenna', img_gray) # 判断键盘按键 key = cv2.waitKey() if key == 27: cv2.destroyAllWindows()
2.截图显示
img_crop = img[0:100, 0:200] cv2.imshow('lena_crop',img_crop) # 判断键盘按键 如果是27 esc 则退出游戏 key = cv2.waitKey() if key == 27: cv2.destroyAllWindows()
3.RGB转换
B,G,R = cv2.split(img) cv2.imshow('B',B) cv2.imshow('G',R) cv2.imshow('R',R) key = cv2.waitKey() if key == 27: cv2.destroyAllWindows()
4.加入滤镜
def random_light_color(img): # brightness B, G, R = cv2.split(img) b_rand = random.randint(-50, 50) if b_rand == 0: pass elif b_rand > 0: lim = 255 - b_rand B[B > lim] = 255 B[B <= lim] = (b_rand + B[B <= lim]).astype(img.dtype) elif b_rand < 0: lim = 0 - b_rand B[B < lim] = 0 B[B >= lim] = (b_rand + B[B >= lim]).astype(img.dtype) g_rand = random.randint(-50, 50) if g_rand == 0: pass elif g_rand > 0: lim = 255 - g_rand G[G > lim] = 255 G[G <= lim] = (g_rand + G[G <= lim]).astype(img.dtype) elif g_rand < 0: lim = 0 - g_rand G[G < lim] = 0 G[G >= lim] = (g_rand + G[G >= lim]).astype(img.dtype) r_rand = random.randint(-50, 50) if r_rand == 0: pass elif r_rand > 0: lim = 255 - r_rand R[R > lim] = 255 R[R <= lim] = (r_rand + R[R <= lim]).astype(img.dtype) elif r_rand < 0: lim = 0 - r_rand R[R < lim] = 0 R[R >= lim] = (r_rand + R[R >= lim]).astype(img.dtype) img_merge = cv2.merge((B, G, R)) #img = cv2.cvtColor(final_hsv, cv2.COLOR_HSV2BGR) return img_merge img_random_color = random_light_color(img) cv2.imshow('img_random_color', img_random_color) key = cv2.waitKey() if key == 27: cv2.destroyAllWindows()
5.gamma校正
def adjust_gamma(image, gamma=1.0): invGamma = 1.0 / gamma table = [] for i in range(256): table.append(((i / 255.0) ** invGamma) * 255) table = np.array(table).astype("uint8") return cv2.LUT(img_dark, table) img_dark = cv2.imread('material/lenna.jpg') cv2.imshow('img_dark', img_dark) img_brighter = adjust_gamma(img_dark, 2) cv2.imshow('img_dark', img_dark) cv2.imshow('img_brighter', img_brighter) key = cv2.waitKey() if key == 27: cv2.destroyAllWindows()
6.图像旋转
M = cv2.getRotationMatrix2D((img.shape[1] / 2, img.shape[0] / 2), 30, 1) # center, angle, scale img_rotate = cv2.warpAffine(img, M, (img.shape[1], img.shape[0])) cv2.imshow('rotated lenna', img_rotate) key = cv2.waitKey(0) if key == 27: cv2.destroyAllWindows()
7.仿射变换
rows, cols, ch = img.shape pts1 = np.float32([[0, 0], [cols - 1, 0], [0, rows - 1]]) pts2 = np.float32([[cols * 0.2, rows * 0.1], [cols * 0.9, rows * 0.2], [cols * 0.1, rows * 0.9]]) M = cv2.getAffineTransform(pts1, pts2) dst = cv2.warpAffine(img, M, (cols, rows)) cv2.imshow('affine lenna', dst) key = cv2.waitKey(0) if key == 27: cv2.destroyAllWindows()
8.透视变化
def random_warp(img, row, col): height, width, channels = img.shape # warp: random_margin = 60 x1 = random.randint(-random_margin, random_margin) y1 = random.randint(-random_margin, random_margin) x2 = random.randint(width - random_margin - 1, width - 1) y2 = random.randint(-random_margin, random_margin) x3 = random.randint(width - random_margin - 1, width - 1) y3 = random.randint(height - random_margin - 1, height - 1) x4 = random.randint(-random_margin, random_margin) y4 = random.randint(height - random_margin - 1, height - 1) dx1 = random.randint(-random_margin, random_margin) dy1 = random.randint(-random_margin, random_margin) dx2 = random.randint(width - random_margin - 1, width - 1) dy2 = random.randint(-random_margin, random_margin) dx3 = random.randint(width - random_margin - 1, width - 1) dy3 = random.randint(height - random_margin - 1, height - 1) dx4 = random.randint(-random_margin, random_margin) dy4 = random.randint(height - random_margin - 1, height - 1) pts1 = np.float32([[x1, y1], [x2, y2], [x3, y3], [x4, y4]]) pts2 = np.float32([[dx1, dy1], [dx2, dy2], [dx3, dy3], [dx4, dy4]]) M_warp = cv2.getPerspectiveTransform(pts1, pts2) img_warp = cv2.warpPerspective(img, M_warp, (width, height)) return M_warp, img_warp M_warp, img_warp = random_warp(img, img.shape[0], img.shape[1]) cv2.imshow('lenna_warp', img_warp) key = cv2.waitKey(0) if key == 27: cv2.destroyAllWindows()
lenna近照
lenna近照
再厉害的图片处理，也抵挡不过时间的威力，将近七旬的“小姐姐”以另一种方式为图片处理领域作出了自己的贡献
致敬
