Use machine epsilon in transform.rowcol (#2106)

* Use machine epsilon.

* Use window rounding methods.

* Update test checksums

* Update test expected value

rasterio/merge.py

@@ -308,15 +308,15 @@ def nullcontext(obj):
             )
             logger.debug("Src %s window: %r", src.name, src_window)
 
-            src_window = src_window.round_shape()
-
             # 3. Compute the destination window
             dst_window = windows.from_bounds(
                 int_w, int_s, int_e, int_n, output_transform, precision=precision
             )
 
             # 4. Read data in source window into temp
-            trows, tcols = (int(round(dst_window.height)), int(round(dst_window.width)))
+            src_window = src_window.round_shape(pixel_precision=0)
+            dst_window = dst_window.round_shape(pixel_precision=0)
+            trows, tcols = dst_window.height, dst_window.width
             temp_shape = (src_count, trows, tcols)
             temp = src.read(
                 out_shape=temp_shape,
@@ -328,9 +328,8 @@ def nullcontext(obj):
             )
 
         # 5. Copy elements of temp into dest
-        roff, coff = (
-            int(round(dst_window.row_off)), int(round(dst_window.col_off)))
-
+        dst_window = dst_window.round_offsets(pixel_precision=0)
+        roff, coff = dst_window.row_off, dst_window.col_off
         region = dest[:, roff:roff + trows, coff:coff + tcols]
 
         if math.isnan(nodataval):

rasterio/transform.py

@@ -2,6 +2,7 @@
 
 from collections.abc import Iterable
 import math
+import sys
 
 from affine import Affine
 
@@ -218,20 +219,13 @@ def rowcol(transform, xs, ys, op=math.floor, precision=None):
         list of column indices
     """
 
-    single_x = False
-    single_y = False
     if not isinstance(xs, Iterable):
         xs = [xs]
-        single_x = True
     if not isinstance(ys, Iterable):
         ys = [ys]
-        single_y = True
-
-    if precision is None:
-        eps = 0.0
-    else:
-        eps = 10.0 ** -precision * (1.0 - 2.0 * op(0.1))
 
+    eps = sys.float_info.epsilon
+
     invtransform = ~transform
 
     rows = []
@@ -241,9 +235,9 @@ def rowcol(transform, xs, ys, op=math.floor, precision=None):
         cols.append(op(fcol))
         rows.append(op(frow))
 
-    if single_x:
+    if len(xs) == 1:
         cols = cols[0]
-    if single_y:
+    if len(ys) == 1:
         rows = rows[0]
 
     return rows, cols

tests/test_rio_merge.py

@@ -453,13 +453,13 @@ def test_merge_tiny_res_bounds(tiffs, runner):
     assert result.exit_code == 0
 
     # Output should be
-    # [[[0  90]
+    # [[[120  90]
     #   [0   0]]]
 
     with rasterio.open(outputname) as src:
         data = src.read()
         print(data)
-        assert data[0, 0, 0] == 0
+        assert data[0, 0, 0] == 120
         assert data[0, 0, 1] == 90
         assert data[0, 1, 0] == 0
         assert data[0, 1, 1] == 0
@@ -481,7 +481,7 @@ def test_merge_rgb(tmpdir, runner):
     assert result.exit_code == 0
 
     with rasterio.open(outputname) as src:
-        assert [src.checksum(i) for i in src.indexes] == [33219, 35315, 45188]
+        assert [src.checksum(i) for i in src.indexes] == [25420, 29131, 37860]
 
 
 def test_merge_tiny_intres(tiffs):