How To Save An Image With The Same Properties As A Different Image

I want to use the properties of a specific image, for example: t0 = cv2.cvtColor(cv2.imread('original.jpg'), cv2.COLOR_BGR2RGB) and save a new image with the same properties. Reph

Solution 1:

AFAIK, you cannot set the dpi when writing a JPEG with OpenCV, so you could maybe "shell out" to exiftool with Python's subprocess command after writing the image with cv2.imwrite():

exiftool -jfif:Xresolution=301 -jfif:Yresolution=302 result.jpg

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As an alternative, this is a rather nasty hack to overwrite the dpi and x-resolution and y-resolution in a JPEG file generated by OpenCV:

#!/usr/bin/env python3import struct
import numpy as np
import cv2

defwriteJPEGwithdpi(im, filename, dpi=(72,72)):
   """Save the image as JPEG with embedded dpi"""# Encode as JPEG into memory
   retval, buffer = cv2.imencode(".jpg", im)
   s = bytearray(buffer)

   # APP0 segment looks like this# 0xFF, 0xE0,                     // APP0 segment# 0x00, 0x10,                     // size of segment, including these 2 bytes; 0x10 = 16 bytes# 0x4A, 0x46, 0x49, 0x46, 0x00,   // identifier string: "JFIF"# 0x01, 0x01,                     // JFIF version 1.01# 0x00,                           // density units (0=no units, 1=dpi)# 0x00, 0x01,                     // horizontal density# 0x00, 0x01,                     // vertical density# 0x00,                           // X thumbnail size# 0x00                            // Y thumbnail size# Find JFIF marker
   JFIF = s.find(b'JFIF\0')

   # Overwrite units, and x-resolution, and y-resolution 
   s[JFIF+7:JFIF+8]   = b'\x01'# density units = 1, i.e. dpi
   s[JFIF+8 :JFIF+10] = (dpi[0]).to_bytes(2, byteorder='big')  # 2 bytes of x-resolution
   s[JFIF+10:JFIF+12] = (dpi[1]).to_bytes(2, byteorder='big')  # 2 bytes of y-resolutionwithopen(filename, "wb") as out:
      out.write(s)

################################################################################# main################################################################################# Load sample image
im = cv2.imread('/Users/mark/sample/images/lena.png')

# Save at specific dpi
writeJPEGwithdpi(im, "result.jpg", (77,309))

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Check result with exiftool:

exiftoolresult.jpgExifTool Version Number         :12.00File Name                       :result.jpgDirectory                       :.File Size                       :105kBFile Modification Date/Time     :2021:02:0814:48:52+00:00File Access Date/Time           :2021:02:0814:48:54+00:00File Inode Change Date/Time     :2021:02:0814:48:52+00:00File Permissions                :rw-r--r--File Type                       :JPEGFile Type Extension             :jpgMIME Type                       :image/jpegJFIF Version                    :1.01Resolution Unit                 :inches<---LOOKSGOODX Resolution                    :77<---LOOKSGOODY Resolution                    :309<---LOOKSGOODImage Width                     :512Image Height                    :512Encoding Process                :BaselineDCT,HuffmancodingBits Per Sample                 :8Color Components                :3Y Cb Cr Sub Sampling            :YCbCr4:2:0(22)Image Size                      :512x512Megapixels                      :0.262

Solution 2:

Use imwrite method from opencv.

import cv2

img='original.jpg'
t0 = cv2.cvtColor(cv2.imread(img), cv2.COLOR_BGR2RGB)

# To save your processed image
cv2.imwrite('img_t0.jpg',t0)

#To save your original file with save properties 
cv2.imwrite('new_original.jpg',img)