implement scaler basd on 'Image Scaling With Bresenham'

1 files changed, 56 insertions, 3 deletions

diff --git a/scaler.c b/scaler.c
index 04e8d22..5fca036 100644
--- a/scaler.c
+++ b/scaler.c
@@ -27,8 +27,61 @@
 #include "scaler.h"
 #include <vdr/osd.h>
 
-cBitmap *cScaler::scaleBitmap(cBitmap *src, uint32_t width, uint32_t height)
+// scaling based on article "Image Scaling With Bresenham" by Thiadmer Riemersma
+// http://www.ddj.com/184405045
+
+static void scaleLine(const tIndex *src, tIndex *dest, int srcWidth, int destWidth)
 {
-    // TODO
-    return NULL;
+    int numPixels = destWidth;
+    int intPart = srcWidth / destWidth;
+    int fractPart = srcWidth % destWidth;
+    int e = 0;
+
+    while (numPixels-- > 0) {
+        *dest++ = *src;
+        src += intPart;
+
+        e += fractPart;
+        if (e >= destWidth) {
+            e -= destWidth;
+            src++;
+        }
+    }
+}
+
+static void scaleRect(const tIndex *src, tIndex *dest, int srcWidth, int srcHeight, int destWidth, int destHeight)
+{
+    int numPixels = destHeight;
+    int intPart = (srcHeight / destHeight) * srcWidth;
+    int fractPart = srcHeight % destHeight;
+    int e = 0;
+
+    while (numPixels-- > 0) {
+
+        scaleLine(src, dest, srcWidth, destWidth);
+
+        dest += destWidth;
+        src += intPart;
+
+        e += fractPart;
+        if (e >= destHeight) {
+            e -= destHeight;
+            src += srcWidth;
+        }
+    }
+}
+
+cBitmap *cScaler::scaleBitmap(cBitmap *source, int width, int height)
+{
+    cBitmap *scaled = new cBitmap(width, height, 4, 0, 0);
+
+    int osdWidth = source->Width();
+    int osdHeight = source->Height();
+
+    const tIndex *src = source->Data(0, 0);
+    tIndex *dest = (tIndex *)scaled->Data(0, 0);
+
+    scaleRect(src, dest, osdWidth, osdHeight, width, height);
+
+    return scaled;
 }