Rotate, Zoom and center the image

Improves the rotation by centering the image on the screen when it is
smaller than the screen size.

Optimal zoom is calculated for images than are higher in hight when
they are rotated as well.

Fixed rotation (anti)clockwise. X, Y axis + angles in gradians are
handled different by cairo.

Signed-off-by: Manuel Kaufmann <humitos@gmail.com>
Signed-off-by: Agustin Zubiaga <aguz@sugarlabs.org>

1 files changed, 80 insertions, 33 deletions

diff --git a/ImageView.py b/ImageView.py
index 30b19ac..cbc5516 100644
--- a/ImageView.py
+++ b/ImageView.py
@@ -27,6 +27,7 @@ import logging
 import cairo
 import random
 import time
+import math
 
 ZOOM_IN_OUT = 0.1
 
@@ -71,6 +72,7 @@ class ImageViewer(Gtk.DrawingArea):
         self._fast = True
         self._redraw_id = None
         self._is_touching = False
+        self._switched = False
 
     def do_get_property(self, pspec):
         if pspec.name == 'zoom':
@@ -123,35 +125,64 @@ class ImageViewer(Gtk.DrawingArea):
         h = int(self.surface.get_height() * self.zoom)
         logging.error('W: %s, H: %s', w, h)
 
-        ctx.save()
         if self._fast:
             ctx.set_antialias(cairo.ANTIALIAS_NONE)
-        if self.angle != 0:
-            logging.error('Rotating: %s', self.angle)
-            ctx.translate(0.5 * w, 0.5 * h)
-            ctx.rotate(self.angle)
-            ctx.translate(-0.5 * w, -0.5 * h)
 
         scrolled_window = self.get_parent()
         rect = scrolled_window.get_allocation()
         x = y = 0
-        if rect.width >= w:
-            x = int((rect.width - w) / 2)
-        elif self._is_touching:
-            hadj = int((w - rect.width) / 2)
-            hadjustment = scrolled_window.get_hadjustment()
-            hadjustment.set_value(hadj)
-
-        if rect.height >= h:
-            y = int((rect.height - h) / 2)
-        elif self._is_touching:
-            vadj = int((h - rect.height) / 2)
-            vadjustment = scrolled_window.get_vadjustment()
-            vadjustment.set_value(vadj)
+        if self.angle != 0:
+            logging.error('Rotating: %s', self.angle)
+            ctx.rotate(self.angle)
+
+            if self.angle == math.pi:
+                ctx.translate(-w, -h)
+
+                if rect.width > w:
+                    x = -(rect.width - w) / 2
+                if rect.height > h:
+                    y = -(rect.height - h) / 2
+
+            elif self.angle == math.pi / 2:
+                ctx.translate(0, -h)
+
+                # center the image
+                if rect.height > w:
+                    x = (rect.height - w) / 2
+                if rect.width > h:
+                    y = -(rect.width - h) / 2
+
+            elif self.angle == math.pi * 3 / 2:
+                ctx.translate(-w, 0)
+
+                if rect.height > w:
+                    x = -(rect.height - w) / 2
+                if rect.width > h:
+                    y = (rect.width - h) / 2
+
+        else:
+            if rect.width > w:
+                x = int((rect.width - w) / 2)
+            if rect.height > h:
+                y = int((rect.height - h) / 2)
+        ctx.translate(x, y)
+
+        if self._is_touching:
+            if self._switched:
+                w, h = h, w
+
+            if rect.height < h:
+                vadj = int((h - rect.height) / 2)
+                vadjustment = scrolled_window.get_vadjustment()
+                vadjustment.set_value(vadj)
+
+            if rect.width < w:
+                hadj = int((w - rect.width) / 2)
+                hadjustment = scrolled_window.get_hadjustment()
+                hadjustment.set_value(hadj)
 
         if self.zoom != 1:
             logging.error('Scaling: %s', self.zoom)
-            ctx.translate(x, y)
             ctx.scale(self.zoom, self.zoom)
 
         ctx.set_source_surface(self.surface, 0, 0)
@@ -171,9 +202,23 @@ class ImageViewer(Gtk.DrawingArea):
     def _redraw_high_quality(self):
         self._fast = False
         self._redraw_id = None
-        self.queue_draw()
+        self._redraw()
         return False
 
+    def _redraw(self):
+        # README: this is a hack to not raise the 'draw' event (again)
+        # when we request more space to show the scroll bars
+        w = int(self.surface.get_width() * self.zoom)
+        h = int(self.surface.get_height() * self.zoom)
+
+        self._switched = False
+        if (self.angle / (math.pi / 2)) % 2 == 1:
+            # change image dimensions if it's rotated
+            w, h = h, w
+            self._switched = True
+
+        self.set_size_request(w, h)
+
     def set_zoom(self, zoom):
         self._optimal_zoom_flag = False
         self._set_zoom(zoom)
@@ -191,8 +236,8 @@ class ImageViewer(Gtk.DrawingArea):
     def set_angle(self, angle):
         self._optimal_zoom_flag = True
 
-        self.angle = angle
-        self.queue_draw()
+        self.angle = angle % (2 * math.pi)
+        self._redraw()
         self.emit('angle-changed')
 
     def zoom_in(self):
@@ -238,11 +283,18 @@ class ImageViewer(Gtk.DrawingArea):
         width = rect.width
         height = rect.height
 
-        if width < self.surface.get_width() or \
-                height < self.surface.get_height():
+        surface_width = self.surface.get_width()
+        surface_height = self.surface.get_height()
+
+        if self._switched:
+            surface_width, surface_height = \
+                surface_height, surface_width
+
+        if width < surface_width or \
+                height < surface_height:
             # Image is larger than allocated size
-            zoom = min(width / self.surface.get_width(),
-                    height / self.surface.get_height())
+            zoom = min(width / surface_width,
+                    height / surface_height)
         else:
             zoom = 1
 
@@ -251,12 +303,7 @@ class ImageViewer(Gtk.DrawingArea):
 
     def _set_zoom(self, zoom):
         self.zoom = zoom
-#        # README: this is a hack to not raise the 'draw' event (again)
-#        # when we request more space to show the scroll bars
-        self._fast = True
-        w = int(self.surface.get_width() * self.zoom)
-        h = int(self.surface.get_height() * self.zoom)
-        self.set_size_request(w, h)
+        self._redraw()
         self.emit('zoom-changed')