[Digikam-devel] extragear/graphics/digikam/utilities/imageeditor/canvas

[Gilles Caulier]

SVN commit 649987 by cgilles:

digiKam from trunk : Image Editor : severe bug fix in canvas :

With implementations <= 0.9.1, the canvas doesn't work properly using high zoom level (> 500). The real image <==> canvas pixmap interface do not compute properlly the tile area values. This provide a lots of  "tile" artefacts over the image. Look the example here:

http://digikam3rdparty.free.fr/Screenshots/editorhighzoomartefact.png

Note than these "tile" artifacts are not the real tiles of canvas and of course not the JPEG artifact (the image is PNG in this screenshot)

The new implementation fix this problem to handle properly the areas to 
use from the source image to generate the canvas pixmap tiles.  

Note to users : i need your feedback to check if all work fine on your computer (to be sure if my patch do not give side effects (:=)))). Thanks in advance...

CCMAIL: digikam-devel at kde.org

 M  +11 -7     canvas.cpp  


--- trunk/extragear/graphics/digikam/utilities/imageeditor/canvas/canvas.cpp #649986:649987
@@ -480,6 +480,7 @@
 
         QPixmap pix(d->tileSize, d->tileSize);
         int sx, sy, sw, sh;
+        int step = (int)floor(d->tileSize / d->zoom); 
 
         for (int j = y1 ; j < y2 ; j += d->tileSize)
         {
@@ -512,15 +513,18 @@
                         pix->fill(d->bgColor);
                     }
 
-                    // FIXME : Marcel, there is a serious problem here with high zoom level (> 500).
-                    // The sx, sy, sw, sh values aren't computed properly and a tile artefact appear 
-                    // over the image. Look the exmaple here:
+                    // NOTE : with implementations <= 0.9.1, the canvas doesn't work properly using high zoom level (> 500).
+                    // The sx, sy, sw, sh values haven't be computed properly and "tile" artefacts been appears 
+                    // over the image. Look the example here:
                     // http://digikam3rdparty.free.fr/Screenshots/editorhighzoomartefact.png
+                    // Note than these "tile" artifacts are not the real tiles of canvas.
+                    // The new implementation below fix this problem to handle properly the areas to 
+                    // use from the source image to generate the canvas pixmap tiles.  
 
-                    sx = (int)floor(i           / d->zoom);
-                    sy = (int)floor(j           / d->zoom);
-                    sw = (int)floor(d->tileSize / d->zoom);
-                    sh = (int)floor(d->tileSize / d->zoom);
+                    sx = (int)floor(((double)i / d->zoom) / (d->tileSize / d->zoom)) * step;
+                    sy = (int)floor(((double)j / d->zoom) / (d->tileSize / d->zoom)) * step;
+                    sw = step;
+                    sh = step;
 
                     if (d->rubber && d->pressedMoved && !d->pressedMoving)
                     {