Convert Between OpenCV and PIL Images | Python
In many circumstances, we need to convert a cv2 image to a PIL image (or PIL to cv2). Here, I will show you how to convert RGB/RGBA/grayscale images from cv2 to PIL or PIL to cv2.
Since the color channels are ordered differently in PIL and cv2 images, we have to convert the color format manually.
| Pillow (PIL) | OpenCV (cv2) | |
|---|---|---|
| Colorful image | RGB | BGR |
| Transparent image | RGBA | BGRA |
1. Colorful Image (RGB)
Pillow to OpenCV
cv2_img = np.array(pil_img)
cv2_img = cv2.cvtColor(cv2_img, cv2.COLOR_RGB2BGR)OpenCV to Pillow
cv2_img = cv2.cvtColor(cv2_img, cv2.COLOR_BGR2RGB)
pil_img = Image.fromarray(cv2_img)2. Transparent Image (RGBA)
Pillow to OpenCV
cv2_img = np.array(pil_img)
cv2_img = cv2.cvtColor(cv2_img, cv2.COLOR_RGBA2BGRA)OpenCV to Pillow
cv2_img = cv2.cvtColor(cv2_img, cv2.COLOR_BGRA2RGBA)
pil_img = Image.fromarray(cv2_img)3. Grayscale Image
Pillow to OpenCV
cv2_img = np.array(pil_img)OpenCV to Pillow
pil_img = Image.fromarray(cv2_img)Full Example
Pillow to OpenCV
import cv2
from PIL import Image
import numpy as np # remember to import numpy
# read images
pil_img_jpg = Image.open("test_images/test1.jpg")
pil_img_png = Image.open("test_images/test2.png")
pil_img_gray = Image.open("test_images/test1.jpg").convert("L")
# convert Pillow (RGB) to OpenCV (BGR)
cv2_img_jpg = np.array(pil_img_jpg)
cv2_img_jpg = cv2.cvtColor(cv2_img_jpg, cv2.COLOR_RGB2BGR)
# convert Pillow (RGBA) to OpenCV (BGRA)
cv2_img_png = np.array(pil_img_png)
cv2_img_png = cv2.cvtColor(cv2_img_png, cv2.COLOR_RGBA2BGRA)
# convert Pillow to OpenCV (grayscale)
cv2_img_gray = np.array(pil_img_gray)OpenCV to Pillow
import cv2
from PIL import Image
import numpy as np # remember to import numpy
# read images
cv2_img_jpg = cv2.imread("test_images/test1.jpg")
cv2_img_png = cv2.imread("test_images/test2.png", cv2.IMREAD_UNCHANGED)
cv2_img_gray = cv2.imread("test_images/test1.jpg", cv2.IMREAD_GRAYSCALE)
# convert OpenCV (BGR) to Pillow (RGB)
cv2_img_jpg = cv2.cvtColor(cv2_img_jpg, cv2.COLOR_BGR2RGB)
pil_img_jpg = Image.fromarray(cv2_img_jpg)
# convert OpenCV (BGRA) to Pillow (RGBA)
cv2_img_png = cv2.cvtColor(cv2_img_png, cv2.COLOR_BGRA2RGBA)
pil_img_png = Image.fromarray(cv2_img_png)
# convert OpenCV to Pillow (grayscale)
pil_img_gray = Image.fromarray(cv2_img_gray)Syntax
cv2.cvtColor(src, code[, dst[, dstCn]])Parameters:
src: input image: 8-bit unsigned, 16-bit unsigned ( CV_16UC… ), or single-precision floating-point.dst: output image of the same size and depth as src.code: color space conversion code (see ColorConversionCodes).dstCn: number of channels in the destination image; if the parameter is 0, the number of channels is derived automatically fromsrcandcode.
Returns:
- The converted image (Numpy array)
