Added resize Mode.BEST_FIT_BOTH to the Scalr engine, ref rkalla#94.

src/main/java/org/imgscalr/Scalr.java

@@ -444,6 +444,12 @@ public static enum Mode {
 		 * how it makes the image look, that is what this mode is for.
 		 */
 		FIT_EXACT,
+		/**
+		 * Used to indicate that the scaling implementation should calculate
+		 * dimensions for the largest image that fit within the bounding box,
+		 * without cropping or distortion, retaining the original proportions.
+		 */
+		BEST_FIT_BOTH,
 		/**
 		 * Used to indicate that the scaling implementation should calculate
 		 * dimensions for the resultant image that best-fit within the given
@@ -1615,7 +1621,24 @@ public static BufferedImage resize(BufferedImage src, Method scalingMethod,
 		 * just specify the dimensions they would like the image to roughly fit
 		 * within and it will do the right thing without mangling the result.
 		 */
-		if (resizeMode != Mode.FIT_EXACT) {
+		if (resizeMode == Mode.FIT_EXACT) {
+			if (DEBUG)
+				log(1,
+						"Resize Mode FIT_EXACT used, no width/height checking or re-calculation will be done.");
+		} else if (resizeMode == Mode.BEST_FIT_BOTH) {
+			float requestedHeightScaling = ((float) targetHeight / (float) currentHeight);
+			float requestedWidthScaling = ((float) targetWidth / (float) currentWidth);
+			float actualScaling = Math.min(requestedHeightScaling, requestedWidthScaling);
+
+			targetHeight = Math.round((float) currentHeight * actualScaling);
+			targetWidth = Math.round((float) currentWidth * actualScaling);
+
+			if (targetHeight == currentHeight && targetWidth == currentWidth)
+				return src;
+
+			if (DEBUG)
+				log(1, "Auto-Corrected width and height based on scalingRatio %d.", actualScaling);
+		} else {
 			if ((ratio <= 1 && resizeMode == Mode.AUTOMATIC)
 					|| (resizeMode == Mode.FIT_TO_WIDTH)) {
 				// First make sure we need to do any work in the first place
@@ -1655,10 +1678,6 @@ public static BufferedImage resize(BufferedImage src, Method scalingMethod,
 							"Auto-Corrected targetWidth [from=%d to=%d] to honor image proportions.",
 							originalTargetWidth, targetWidth);
 			}
-		} else {
-			if (DEBUG)
-				log(1,
-						"Resize Mode FIT_EXACT used, no width/height checking or re-calculation will be done.");
 		}
 
 		// If AUTOMATIC was specified, determine the real scaling method.

src/test/java/org/imgscalr/ScalrResizeTest.java

@@ -159,4 +159,56 @@ public void testResizeFitExact() {
 		Assert.assertEquals(i2.getWidth(), 500);
 		Assert.assertEquals(i2.getHeight(), 250);
 	}
+
+    @Test
+    public void testResizeAutoVsFitBoth() {
+        // FitBoth will not allow the minor axis to grow beyond the specified box. The four commented
+        // tests show how this interacts
+
+        // For landscape images, AUTO will let targetWidth decide scaling, even if targetHeight is violated
+        BufferedImage landscape = new BufferedImage(500, 250, BufferedImage.TYPE_INT_RGB);
+        testResizeAutoVsBoth(landscape, 500, 250, 500, 250, 500, 250);
+        testResizeAutoVsBoth(landscape, 500, 500, 500, 250, 500, 250);
+
+        testResizeAutoVsBoth(landscape, 800, 300, 800, 400, 600, 300);  // FitBoth restricts y to 300, and adjusts x
+        testResizeAutoVsBoth(landscape, 800, 400, 800, 400, 800, 400);
+        testResizeAutoVsBoth(landscape, 800, 500, 800, 400, 800, 400);
+
+        testResizeAutoVsBoth(landscape, 250, 150, 250, 125, 250, 125);
+        testResizeAutoVsBoth(landscape, 250, 125, 250, 125, 250, 125);
+        testResizeAutoVsBoth(landscape, 250, 100, 250, 125, 200, 100);  // FitBoth imposes smaller y, and adjusts x
+
+        // For portrait images, AUTO will let targetHeight decide scaling, even if targetWidth is violated
+        BufferedImage portrait = new BufferedImage(250, 500, BufferedImage.TYPE_INT_RGB);
+        testResizeAutoVsBoth(portrait, 250, 500, 250, 500, 250, 500);
+        testResizeAutoVsBoth(portrait, 500, 500, 250, 500, 250, 500);
+
+        testResizeAutoVsBoth(portrait, 300, 800, 400, 800, 300, 600);   // FitBoth restricts x to 800, and adjusts y
+        testResizeAutoVsBoth(portrait, 400, 800, 400, 800, 400, 800);
+        testResizeAutoVsBoth(portrait, 500, 800, 400, 800, 400, 800);
+
+        testResizeAutoVsBoth(portrait, 150, 250, 125, 250, 125, 250);
+        testResizeAutoVsBoth(portrait, 125, 250, 125, 250, 125, 250);
+        testResizeAutoVsBoth(portrait, 100, 250, 125, 250, 100, 200);   // FitBoth imposes smaller xj, and adjusts y
+
+        // Squares are treated as a landscape
+        BufferedImage square = new BufferedImage(500, 500, BufferedImage.TYPE_INT_RGB);
+        testResizeAutoVsBoth(square, 500, 500, 500, 500, 500, 500);
+        testResizeAutoVsBoth(square, 800, 800, 800, 800, 800, 800);
+        testResizeAutoVsBoth(square, 400, 400, 400, 400, 400, 400);
+        testResizeAutoVsBoth(square, 800, 600, 800, 800, 600, 600);     // FixBoth restricts both dimensions
+
+    }
+
+    // resize to (w,h) using AUTO and FIT_BOTH modes, then compare auto (w,h) and fitBoth (w,h)
+    private void testResizeAutoVsBoth (BufferedImage i, int targetWidth, int targetHeight, int autoWidth, int autoHeight, int fitBothWidth, int fitBothHeight) {
+        BufferedImage auto = Scalr.resize(i, Mode.AUTOMATIC, targetWidth, targetHeight);
+        BufferedImage fitBoth = Scalr.resize(i, Mode.BEST_FIT_BOTH, targetWidth, targetHeight);
+
+        Assert.assertEquals (autoWidth, auto.getWidth());
+        Assert.assertEquals(autoHeight, auto.getHeight());
+
+        Assert.assertEquals(fitBothWidth, fitBoth.getWidth());
+        Assert.assertEquals(fitBothHeight, fitBoth.getHeight());
+    }
 }