Fix image post-processing for OWLv2

docs/source/en/tasks/zero_shot_object_detection.md

@@ -193,6 +193,29 @@ boxes have the correct coordinates relative to the original image:
      <img src="https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/transformers/tasks/zero-sh-obj-detection_4.png" alt="Beach photo with detected objects"/>
 </div>
 
+Note that for OWLv2, if the image is not square, the coorindates in the lesser dimension are off by a ratio of the lesser dimension to the greater dimension. This is a workaround to correct the coordinates:
+
+```py
+>>> width, height = im.size
+>>> width_ratio = 1
+>>> height_ratio = 1
+
+>>> if width < height:
+...     width_ratio = width / height
+... elif height < width:
+...     height_ratio = height / width
+
+>>> for box, score, label in zip(boxes, scores, labels):
+...     xmin, ymin, xmax, ymax = box
+...     xmin /= width_ratio
+...     ymin /= height_ratio
+...     xmax /= width_ratio
+...     ymax /= height_ratio
+...     draw.rectangle((xmin, ymin, xmax, ymax), outline="red", width=1)
+...     draw.text((xmin, ymin), f"{text_queries[label]}: {round(score,2)}", fill="white")
+
+>>> im
+```
 ## Batch processing
 
 You can pass multiple sets of images and text queries to search for different (or same) objects in several images.