Resize of pillow in python gives different results

[codeblocker-locc]

cpp code :
#include <PillowResize/PillowResize.hpp>
#include <opencv2/opencv.hpp>
#include
int main()
{
cv::Mat image = cv::imread("/docker/output_detection_1.png", cv::IMREAD_UNCHANGED);
cv::cvtColor(image, image, cv::COLOR_BGR2RGB);

      int target_size = 224;
      std::cout << "Size of image in function : " << image.size() << std::endl;
      cv::Size dst_size(target_size, target_size);
      int filter = cv::INTER_LINEAR;
      image = PillowResize::resize(image, dst_size, filter);
  return 0;
  }

Python Code :
from PIL import Image
import numpy as np
image = Image.open("/workspace/output_detection_1.png")
image = image.convert("RGB")
resized_image = image.resize((224, 224), Image.BILINEAR )

I have dumped the resized image numpy array in file and got significant diff in both the arrays when comparing both the images.

[marcov868]

It is likely caused by a mismatch between the value of the filter you are using in C++. As stated in the docs, PillowResize::resize uses values from the enum PillowResize::InterpolationMethods, which has a 1:1 mapping with the resampling filters enum from PIL.
Instead, the cv::InterpolationFlags has a different enumeration, so you are not actually applying the bilinear interpolation but the Lanczos one.

Can you try changing your code to something like this?

{
      cv::Mat image = cv::imread("/docker/output_detection_1.png", cv::IMREAD_UNCHANGED);
      cv::cvtColor(image, image, cv::COLOR_BGR2RGB);

      int target_size = 224;
      std::cout << "Size of image in function : " << image.size() << std::endl;
      cv::Size dst_size(target_size, target_size);
      int filter = PillowResize::InterpolationMethods::INTERPOLATION_BILINEAR;  // <-- value from PillowResize::InterpolationMethods
      image = PillowResize::resize(image, dst_size, filter);
      return 0;
  }