fix export_to_png with img_sdl2

Author: kived

kivy/core/image/_img_sdl2.pyx

@@ -23,14 +23,16 @@ def init():
 
     _is_init = 1
 
-
 def save(filename, w, h, fmt, pixels, flipped):
     # this only saves in png for now.
     cdef bytes c_filename = filename.encode('utf-8')
     cdef int pitch
     pitch = w * 4
 
-    cdef SDL_Surface *image = SDL_CreateRGBSurfaceFrom(<void *>pixels, w, h, 32, pitch, 0x00000000ff, 0x0000ff00, 0x00ff0000, 0xff000000)
+    if flipped:
+        Logger.warn(
+            'ImageSDL2: saving flipped textures not supported; image will be flipped')
+    cdef SDL_Surface *image = SDL_CreateRGBSurfaceFrom(<void *>pixels + 36, w, h, 32, pitch, 0x00000000ff, 0x0000ff00, 0x00ff0000, 0xff000000)
 
     IMG_SavePNG(image, c_filename)
     SDL_FreeSurface(image)

kivy/uix/widget.py

@@ -172,7 +172,7 @@ def on_touch_down(self, touch, after=False):
 from kivy.properties import (NumericProperty, StringProperty, AliasProperty,
                              ReferenceListProperty, ObjectProperty,
                              ListProperty, DictProperty, BooleanProperty)
-from kivy.graphics import Canvas, Translate, Fbo, ClearColor, ClearBuffers
+from kivy.graphics import Canvas, Translate, Fbo, ClearColor, ClearBuffers, Scale
 from kivy.base import EventLoop
 from kivy.lang import Builder
 from kivy.context import get_current_context
@@ -555,11 +555,12 @@ def export_to_png(self, filename, *args):
         with fbo:
             ClearColor(0, 0, 0, 1)
             ClearBuffers()
-            Translate(-self.x, -self.y, 0)
+            Scale(1, -1, 1)
+            Translate(-self.x, -self.y - self.height, 0)
 
         fbo.add(self.canvas)
         fbo.draw()
-        fbo.texture.save(filename)
+        fbo.texture.save(filename, flipped=False)
         fbo.remove(self.canvas)
 
         if self.parent is not None: