diff --git a/testsuite/oiiotool-demosaic/ref/out.txt b/testsuite/oiiotool-demosaic/ref/out.txt
index 22c9be59fc..95a9f7e731 100644
--- a/testsuite/oiiotool-demosaic/ref/out.txt
+++ b/testsuite/oiiotool-demosaic/ref/out.txt
@@ -1,64 +1,64 @@
-Computing diff of "testimage_float.exr" vs "result_float_RGGB-linear.exr"
+Computing diff of "testimage.exr" vs "result_float_RGGB-linear.exr"
 PASS
-Computing diff of "testimage_float.exr" vs "result_float_GRBG-linear.exr"
+Computing diff of "testimage.exr" vs "result_float_GRBG-linear.exr"
 PASS
-Computing diff of "testimage_float.exr" vs "result_float_GBRG-linear.exr"
+Computing diff of "testimage.exr" vs "result_float_GBRG-linear.exr"
 PASS
-Computing diff of "testimage_float.exr" vs "result_float_BGGR-linear.exr"
+Computing diff of "testimage.exr" vs "result_float_BGGR-linear.exr"
 PASS
-Computing diff of "testimage_float.exr" vs "result_float_RGGB-MHC.exr"
+Computing diff of "testimage.exr" vs "result_float_RGGB-MHC.exr"
 PASS
-Computing diff of "testimage_float.exr" vs "result_float_GRBG-MHC.exr"
+Computing diff of "testimage.exr" vs "result_float_GRBG-MHC.exr"
 PASS
-Computing diff of "testimage_float.exr" vs "result_float_GBRG-MHC.exr"
+Computing diff of "testimage.exr" vs "result_float_GBRG-MHC.exr"
 PASS
-Computing diff of "testimage_float.exr" vs "result_float_BGGR-MHC.exr"
+Computing diff of "testimage.exr" vs "result_float_BGGR-MHC.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_RGGB-linear.exr"
+Computing diff of "testimage.exr" vs "result_half_RGGB-linear.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_GRBG-linear.exr"
+Computing diff of "testimage.exr" vs "result_half_GRBG-linear.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_GBRG-linear.exr"
+Computing diff of "testimage.exr" vs "result_half_GBRG-linear.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_BGGR-linear.exr"
+Computing diff of "testimage.exr" vs "result_half_BGGR-linear.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_RGGB-MHC.exr"
+Computing diff of "testimage.exr" vs "result_half_RGGB-MHC.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_GRBG-MHC.exr"
+Computing diff of "testimage.exr" vs "result_half_GRBG-MHC.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_GBRG-MHC.exr"
+Computing diff of "testimage.exr" vs "result_half_GBRG-MHC.exr"
 PASS
-Computing diff of "testimage_half.exr" vs "result_half_BGGR-MHC.exr"
+Computing diff of "testimage.exr" vs "result_half_BGGR-MHC.exr"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_RGGB-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_RGGB-linear.tiff"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_GRBG-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_GRBG-linear.tiff"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_GBRG-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_GBRG-linear.tiff"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_BGGR-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_BGGR-linear.tiff"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_RGGB-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_RGGB-MHC.tiff"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_GRBG-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_GRBG-MHC.tiff"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_GBRG-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_GBRG-MHC.tiff"
 PASS
-Computing diff of "testimage_uint16.tiff" vs "result_uint16_BGGR-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint16_BGGR-MHC.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_RGGB-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_RGGB-linear.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_GRBG-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_GRBG-linear.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_GBRG-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_GBRG-linear.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_BGGR-linear.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_BGGR-linear.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_RGGB-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_RGGB-MHC.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_GRBG-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_GRBG-MHC.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_GBRG-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_GBRG-MHC.tiff"
 PASS
-Computing diff of "testimage_uint8.tiff" vs "result_uint8_BGGR-MHC.tiff"
+Computing diff of "testimage.exr" vs "result_uint8_BGGR-MHC.tiff"
 PASS
diff --git a/testsuite/oiiotool-demosaic/run.py b/testsuite/oiiotool-demosaic/run.py
index f1698d0e36..773d9487da 100755
--- a/testsuite/oiiotool-demosaic/run.py
+++ b/testsuite/oiiotool-demosaic/run.py
@@ -23,10 +23,6 @@
     "BGGR": make_pattern_BGGR
 }
 
-# Create a test image with color gradients
-make_testimage = f"--pattern fill:topleft=0,0,1:topright=0,1,0:bottomleft=1,0,1:bottomright=1,1,0 {width}x{height} 3 "
-
-
 types = [
     {
         "type" : "float",
@@ -51,6 +47,18 @@
 ]
 
     
+# Create a test image with color gradient
+make_testimage = f"--pattern fill:topleft=0,0,1:topright=0,1,0:bottomleft=1,0,1:bottomright=1,1,0 {width}x{height} 3 "
+command += oiiotool (make_testimage + f" -o:type=float testimage.exr")
+
+# For each Bayer pattern (RGGB, RGRB, GBRG, BGGR), create an image with that
+# pure pattern ({pattern}.exr), then multiply it by the test image and take
+# the channel sum to get a Bayer mosaic image ({pattern}-bayer.exr).
+# This is somewhat expensive, so we do it only once (for float) and then will
+# convert it to the appropriate type upon input.
+for pattern, maker in layouts.items():
+    command += oiiotool (f"{maker} -o:type=float pattern_{pattern}.exr testimage.exr -mul -chsum -o:type=float bayer_{pattern}.exr")
+
 
 for dict in types:
 
@@ -58,22 +66,13 @@
     ext = dict["ext"]
     threshold = dict["threshold"]
 
-    command += oiiotool (make_testimage + f" -o:type={type} testimage_{type}.{ext}")
-
-    # For each Bayer pattern (RGGB, RGRB, GBRG, BGGR), create an image with that
-    # pure pattern ({pattern}.exr), then multiply it by the test image and take
-    # the channel sum to get a Bayer mosaic image ({pattern}-bayer.exr).
-    for pattern, maker in layouts.items():
-        command += oiiotool (f"{maker} -o:type={type} pattern_{type}_{pattern}.{ext} testimage_{type}.{ext} -mul -chsum -o:type={type} bayer_{type}_{pattern}.{ext}")
-
     test = f" --fail {threshold} --hardfail {threshold} --warn {threshold} --diff "
 
-
     # For each algorithm, try demosaicing each pattern test image and compare to
     # the original test image.
     for algo in ['linear', 'MHC']:
         for pattern, maker in layouts.items():
-            command += oiiotool (f"-i:type={type} testimage_{type}.{ext} -i:type={type} bayer_{type}_{pattern}.{ext} --demosaic:algorithm={algo}:layout={pattern} -o:type={type} result_{type}_{pattern}-{algo}.{ext} ")
+            command += oiiotool (f"-i:type={type} testimage.exr -i:type={type} bayer_{pattern}.exr --demosaic:algorithm={algo}:layout={pattern} -o:type={type} result_{type}_{pattern}-{algo}.{ext} ")
             
             crop = 2
             
@@ -82,4 +81,4 @@
             else:
                 cut_cmd = ""
                         
-            command += oiiotool (f"testimage_{type}.{ext} " + cut_cmd + f"result_{type}_{pattern}-{algo}.{ext} " + cut_cmd + test)
+            command += oiiotool (f"testimage.exr " + cut_cmd + f"result_{type}_{pattern}-{algo}.{ext} " + cut_cmd + test)