From 48a62940c0a44047a4c2f1d92c688db031fc33e8 Mon Sep 17 00:00:00 2001
From: "ogueler@idiap.ch" <ogueler@vws110.idiap.ch>
Date: Mon, 3 Apr 2023 01:02:14 +0200
Subject: [PATCH] Added 24bit RGB to 8bit greyscale transformation
---
src/ptbench/data/transforms.py | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/src/ptbench/data/transforms.py b/src/ptbench/data/transforms.py
index c1f1f7d0..993839df 100644
--- a/src/ptbench/data/transforms.py
+++ b/src/ptbench/data/transforms.py
@@ -41,6 +41,29 @@ class SingleAutoLevel16to8:
).astype("uint8"),
).convert("L")
+class RGBtoGreyscale8bit:
+ """Converts a 24-bit RGB image to an 8-bit greyscale representation.
+
+ This transform assumes that the input image is RGB with 24 bits.
+
+ Converts the RGB image to a greyscale image using the well-known formula:
+ Y = 0.299 * R + 0.587 * G + 0.114 * B
+ This formula is based on the relative luminance of the RGB channels in the sRGB color space
+
+ consider such a range should be mapped to the [0,255] range of the
+ destination image.
+ """
+
+ def __call__(self, img):
+ # Use the formula to convert the RGB image to a greyscale image
+ img_array = numpy.array(img).astype(float)
+ grey_array = 0.299 * img_array[:, :, 0] + 0.587 * img_array[:, :, 1] + 0.114 * img_array[:, :, 2]
+
+ # Normalize the greyscale image to the range [0, 255] and convert it to uint8
+ grey_array = numpy.round(255.0 * (grey_array - grey_array.min()) / (grey_array.max() - grey_array.min())).astype('uint8')
+
+ # Create a new greyscale PIL image from the normalized array
+ return PIL.Image.fromarray(grey_array).convert("L")
class RemoveBlackBorders:
"""Remove black borders of CXR."""
--
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