Shuffle all 4(or 9) images in mosaic augmentation (ultralytics#4787)

Thank you for sharing nice open-source codes 👍

I applied to shuffle the order of all 4(or 9) images in mosaic augmentation

Currently, the order of images in mosaic augmentation is not completely random.
The remaining images except the first are randomly arranged. Apply shuffle all to increase the diversity of data composition.

utils/datasets.py

@@ -661,6 +661,7 @@ def load_mosaic(self, index):
     s = self.img_size
     yc, xc = [int(random.uniform(-x, 2 * s + x)) for x in self.mosaic_border]  # mosaic center x, y
     indices = [index] + random.choices(self.indices, k=3)  # 3 additional image indices
+    random.shuffle(indices)
     for i, index in enumerate(indices):
         # Load image
         img, _, (h, w) = load_image(self, index)
@@ -717,6 +718,7 @@ def load_mosaic9(self, index):
     labels9, segments9 = [], []
     s = self.img_size
     indices = [index] + random.choices(self.indices, k=8)  # 8 additional image indices
+    random.shuffle(indices)
     for i, index in enumerate(indices):
         # Load image
         img, _, (h, w) = load_image(self, index)