From 44448b2f4c6a330b6a4df57b62b9908976e30b22 Mon Sep 17 00:00:00 2001
From: Aaron Hopkins <github@die.net>
Date: Tue, 31 Jul 2018 20:30:33 -0700
Subject: [PATCH] Fix sobel implementation.

---
 cmd/fotomat/version.go |  2 +-
 vips/convolution.h     | 20 ++++++++++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/cmd/fotomat/version.go b/cmd/fotomat/version.go
index c6ae214..3875f87 100644
--- a/cmd/fotomat/version.go
+++ b/cmd/fotomat/version.go
@@ -2,5 +2,5 @@ package main
 
 const (
 	// FotomatVersion is updated by git-hooks/pre-commit
-	FotomatVersion = "2.8.241"
+	FotomatVersion = "2.8.242"
 )
diff --git a/vips/convolution.h b/vips/convolution.h
index efa8b14..9b8c0ff 100644
--- a/vips/convolution.h
+++ b/vips/convolution.h
@@ -59,18 +59,26 @@ cgo_sobel(VipsImage *in, VipsImage **out) {
 
     VipsImage *sx = NULL;
     VipsImage *sy = NULL;
+    VipsImage *ax = NULL;
+    VipsImage *ay = NULL;
     VipsImage *add = NULL;
 
     int ret = -1;
     if (!vips_conv(band, &sx, x, NULL)) {
-        if (!vips_conv(band, &sy, y, NULL)) {
-            if (!vips_add(sx, sy, &add, NULL)) {
-                if (!vips_cast(add, out, VIPS_FORMAT_UCHAR, NULL)) {
-                    ret = 0;
+        if (!vips_abs(sx, &ax, NULL)) {
+            if (!vips_conv(band, &sy, y, NULL)) {
+                if (!vips_abs(sy, &ay, NULL)) {
+                    if (!vips_add(ax, ay, &add, NULL)) {
+                        if (!vips_cast(add, out, VIPS_FORMAT_UCHAR, NULL)) {
+                            ret = 0;
+                        }
+                        g_object_unref(add);
+                    }
+                    g_object_unref(ay);
                 }
-                g_object_unref(add);
+                g_object_unref(sy);
             }
-            g_object_unref(sy);
+            g_object_unref(ax);
         }
         g_object_unref(sx);
     }