#### Question about code fragment in features.geometry_window()

Shinji Suzuki

Hi.
Starting this line, bounds extended by (pad_x, pad_y) are computed and
later get transformed.
https://github.com/mapbox/rasterio/blob/master/rasterio/features.py#L451

What I don't understand are;
1. 'pad_x' is subtracted from 'bottom'. Shouldn't 'pad_y' be the one
that should be related to 'bottom'?
2. Same value is computed twice.(e.g. left - pad_x). Since the
computed values are used later only for obtaining max and min. There
are no point in yielding a value multiple times.

If my understanding is correct that this code is for computing the
bounding box after transformation, should not this be changed as
follows?

diff --git a/rasterio/features.py b/rasterio/features.py
index 768f6429..e0764e63 100644
--- a/rasterio/features.py
+++ b/rasterio/features.py
@@ -451,12 +451,12 @@ def geometry_window(
xs = [
x
for (left, bottom, right, top) in all_bounds
- for x in (left - pad_x, right + pad_x, right + pad_x, left - pad_x)
+ for x in (left - pad_x, right + pad_x, right - pad_x, left + pad_x)
]
ys = [
y
for (left, bottom, right, top) in all_bounds
- for y in (top + pad_y, top + pad_y, bottom - pad_x, bottom - pad_x)
+ for y in (top + pad_y, top - pad_y, bottom - pad_y, bottom + pad_y)
]

rows1, cols1 = rowcol(

Thank you for reading.

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