Index: reactos/dll/win32/shimgvw/shimgvw.c
===================================================================
--- reactos/dll/win32/shimgvw/shimgvw.c	(revision 73640)
+++ reactos/dll/win32/shimgvw/shimgvw.c	(working copy)
@@ -2,10 +2,12 @@
  * PROJECT:         ReactOS Picture and Fax Viewer
  * FILE:            dll/win32/shimgvw/shimgvw.c
  * PURPOSE:         shimgvw.dll
- * PROGRAMMER:      Dmitry Chapyshev (dmitry@reactos.org)
+ * PROGRAMMERS:     Dmitry Chapyshev (dmitry@reactos.org)
+ *                  Katayama Hirofumi MZ (katayama.hirofumi.mz@gmail.com)
  *
  * UPDATE HISTORY:
  *      28/05/2008  Created
+ *      16/01/2017  Implemented Zooming by katahiromz
  */
 
 #define WIN32_NO_STATUS
@@ -41,6 +43,60 @@
 
 HWND hDispWnd, hToolBar;
 
+/* zooming */
+#define MIN_ZOOM 10
+#define MAX_ZOOM 1600
+UINT nZoomPercents = 100;
+static const UINT aZoomPercents[] =
+{
+    10, 25, 50, 100, 200, 400, 800, 1600
+};
+
+static void ZoomIn(void)
+{
+    INT i;
+    for (i = 0; i < ARRAYSIZE(aZoomPercents); ++i)
+    {
+        if (nZoomPercents < aZoomPercents[i])
+            break;
+    }
+    if (i == ARRAYSIZE(aZoomPercents))
+        nZoomPercents = MAX_ZOOM;
+    else
+        nZoomPercents = aZoomPercents[i];
+
+    SendMessage(hToolBar, TB_ENABLEBUTTON, IDC_ZOOMM, TRUE);
+    if (nZoomPercents >= MAX_ZOOM)
+        SendMessage(hToolBar, TB_ENABLEBUTTON, IDC_ZOOMP, FALSE);
+    else
+        SendMessage(hToolBar, TB_ENABLEBUTTON, IDC_ZOOMP, TRUE);
+
+    InvalidateRect(hDispWnd, NULL, TRUE);
+}
+
+static void ZoomOut(void)
+{
+    INT i;
+    for (i = ARRAYSIZE(aZoomPercents); i > 0; )
+    {
+        --i;
+        if (aZoomPercents[i] < nZoomPercents)
+            break;
+    }
+    if (i < 0)
+        nZoomPercents = MIN_ZOOM;
+    else
+        nZoomPercents = aZoomPercents[i];
+
+    SendMessage(hToolBar, TB_ENABLEBUTTON, IDC_ZOOMP, TRUE);
+    if (nZoomPercents <= MIN_ZOOM)
+        SendMessage(hToolBar, TB_ENABLEBUTTON, IDC_ZOOMM, FALSE);
+    else
+        SendMessage(hToolBar, TB_ENABLEBUTTON, IDC_ZOOMM, TRUE);
+
+    InvalidateRect(hDispWnd, NULL, TRUE);
+}
+
 /* ToolBar Buttons */
 static const TBBUTTON Buttons [] =
 {   /* iBitmap,     idCommand,   fsState,         fsStyle,     bReserved[2], dwData, iString */
@@ -166,6 +222,8 @@
     WCHAR szTitleBuf[800];
     WCHAR szResStr[512];
     WCHAR *c;
+    RECT Rect;
+    UINT ImageWidth, ImageHeight;
 
     if (node)
     {
@@ -185,6 +243,26 @@
         }
 
         pLoadImage(node->FileName);
+
+        /* calculate zoom percents */
+        GetClientRect(hDispWnd, &Rect);
+        GdipGetImageWidth(image, &ImageWidth);
+        GdipGetImageHeight(image, &ImageHeight);
+        if (ImageHeight * Rect.right < Rect.bottom * ImageWidth)
+        {
+            if (Rect.right < ImageWidth)
+                nZoomPercents = (Rect.right * 100) / ImageWidth;
+            else
+                nZoomPercents = 100;
+        }
+        else
+        {
+            if (Rect.bottom < ImageHeight)
+                nZoomPercents = (Rect.bottom * 100) / ImageHeight;
+            else
+                nZoomPercents = 100;
+        }
+
         InvalidateRect(hDispWnd, NULL, TRUE);
         UpdateWindow(hDispWnd);
     }
@@ -330,8 +408,8 @@
 ImageView_DrawImage(HWND hwnd)
 {
     GpGraphics *graphics;
-    UINT uImgWidth, uImgHeight;
-    UINT height = 0, width = 0, x = 0, y = 0;
+    UINT ImageWidth, ImageHeight;
+    INT ZoomedWidth, ZoomedHeight, x, y;
     PAINTSTRUCT ps;
     RECT rect;
     HDC hdc;
@@ -350,38 +428,37 @@
         return;
     }
 
-    GdipGetImageWidth(image, &uImgWidth);
-    GdipGetImageHeight(image, &uImgHeight);
+    GdipGetImageWidth(image, &ImageWidth);
+    GdipGetImageHeight(image, &ImageHeight);
 
     if (GetClientRect(hwnd, &rect))
     {
         FillRect(hdc, &rect, (HBRUSH)GetStockObject(WHITE_BRUSH));
 
-        if ((rect.right >= uImgWidth)&&(rect.bottom >= uImgHeight))
+        ZoomedWidth = (ImageWidth * nZoomPercents) / 100;
+        ZoomedHeight = (ImageHeight * nZoomPercents) / 100;
+
+        x = (rect.right - ZoomedWidth) / 2;
+        y = (rect.bottom - ZoomedHeight) / 2;
+
+        DPRINT("x = %d, y = %d, ImageWidth = %u, ImageHeight = %u\n");
+        DPRINT("rect.right = %ld, rect.bottom = %ld\n", rect.right, rect.bottom);
+        DPRINT("nZoomPercents = %d, ZoomedWidth = %d, ZoomedHeight = %d\n",
+               nZoomPercents, ZoomedWidth, ZoomedWidth);
+
+        if (nZoomPercents % 100 == 0)
         {
-            width = uImgWidth;
-            height = uImgHeight;
+            GdipSetInterpolationMode(graphics, InterpolationModeNearestNeighbor);
+            GdipSetSmoothingMode(graphics, SmoothingModeNone);
         }
         else
         {
-            height = uImgHeight * (UINT)rect.right / uImgWidth;
-            if (height <= rect.bottom)
-            {
-                width = rect.right;
-            }
-            else
-            {
-                width = uImgWidth * (UINT)rect.bottom / uImgHeight;
-                height = rect.bottom;
-            }
+            GdipSetInterpolationMode(graphics, InterpolationModeHighQualityBilinear);
+            GdipSetSmoothingMode(graphics, SmoothingModeHighQuality);
         }
 
-        y = (rect.bottom / 2) - (height / 2);
-        x = (rect.right / 2) - (width / 2);
-
-        DPRINT("x = %d\ny = %d\nWidth = %d\nHeight = %d\n\nrect.right = %d\nrect.bottom = %d\n\nuImgWidth = %d\nuImgHeight = %d\n", x, y, width, height, rect.right, rect.bottom, uImgWidth, uImgHeight);
-        Rectangle(hdc, x - 1, y - 1, x + width + 1, y + height + 1);
-        GdipDrawImageRect(graphics, image, x, y, width, height);
+        Rectangle(hdc, x - 1, y - 1, x + ZoomedWidth + 1, y + ZoomedHeight + 1);
+        GdipDrawImageRectI(graphics, image, x, y, ZoomedWidth, ZoomedHeight);
     }
     GdipDeleteGraphics(graphics);
     EndPaint(hwnd, &ps);
@@ -524,6 +601,19 @@
     ImageView_CreateToolBar(hwnd);
 }
 
+static VOID
+ImageView_OnMouseWheel(HWND hwnd, INT x, INT y, INT zDelta, UINT fwKeys)
+{
+    if (zDelta < 0)
+    {
+        ZoomOut();
+    }
+    else if (zDelta > 0)
+    {
+        ZoomIn();
+    }
+}
+
 LRESULT CALLBACK
 ImageView_WndProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam)
 {
@@ -567,10 +657,14 @@
 
                 break;
                 case IDC_ZOOMP:
-
+                {
+                    ZoomIn();
+                }
                 break;
                 case IDC_ZOOMM:
-
+                {
+                    ZoomOut();
+                }
                 break;
                 case IDC_SAVE:
                     pSaveImageAs(hwnd);
@@ -597,6 +691,12 @@
         }
         break;
 
+        case WM_MOUSEWHEEL:
+            ImageView_OnMouseWheel(hwnd,
+                (SHORT)LOWORD(lParam), (SHORT)HIWORD(lParam),
+                (SHORT)HIWORD(wParam), (UINT)LOWORD(wParam));
+            break;
+
         case WM_NOTIFY:
         {
             LPNMHDR pnmhdr = (LPNMHDR)lParam;