Add guards to prevent making BufferedImage with custom image type.

Previous commit caused certain unit tests to fail in Java 5, as PNGs
were loaded on `BufferedImage` with `.TYPE_CUSTOM`.

src/main/java/net/coobird/thumbnailator/builders/BufferedImageBuilder.java

@@ -115,9 +115,15 @@ public BufferedImage build() {
 	 * Sets the type of the image of the {@link BufferedImage}.
 	 * 
 	 * @param imageType		The image type to use.
+	 * 						If {@link BufferedImage#TYPE_CUSTOM} is used, it
+	 * 						be substituted by {@link BufferedImage#TYPE_INT_ARGB}.
 	 * @return				This {@link BufferedImageBuilder} instance.
 	 */
 	public BufferedImageBuilder imageType(int imageType) {
+		if (imageType == BufferedImage.TYPE_CUSTOM) {
+			imageType = DEFAULT_TYPE;
+		}
+
 		this.imageType = imageType;
 		return this;
 	}

src/main/java/net/coobird/thumbnailator/filters/Canvas.java

@@ -29,6 +29,7 @@
 import java.awt.Point;
 import java.awt.image.BufferedImage;
 
+import net.coobird.thumbnailator.builders.BufferedImageBuilder;
 import net.coobird.thumbnailator.geometry.Position;
 
 /**
@@ -171,8 +172,11 @@ public BufferedImage apply(BufferedImage img) {
 				0, 0, 0, 0
 		);
 
-		BufferedImage finalImage =
-			new BufferedImage(widthToUse, heightToUse, img.getType());
+		BufferedImage finalImage = new BufferedImageBuilder(
+				widthToUse,
+				heightToUse,
+				img.getType()
+		).build();
 
 		Graphics g = finalImage.getGraphics();
 

src/main/java/net/coobird/thumbnailator/filters/Transparency.java

@@ -24,6 +24,7 @@
 
 package net.coobird.thumbnailator.filters;
 
+import net.coobird.thumbnailator.builders.BufferedImageBuilder;
 import net.coobird.thumbnailator.util.BufferedImages;
 
 import java.awt.AlphaComposite;
@@ -85,8 +86,11 @@ public BufferedImage apply(BufferedImage img) {
 		int width = img.getWidth();
 		int height = img.getHeight();
 
-		BufferedImage finalImage =
-			new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
+		BufferedImage finalImage = new BufferedImageBuilder(
+				width,
+				height,
+				BufferedImage.TYPE_INT_ARGB
+		).build();
 
 		Graphics2D g = finalImage.createGraphics();
 		g.setComposite(composite);

src/main/java/net/coobird/thumbnailator/resizers/ProgressiveBilinearResizer.java

@@ -24,6 +24,8 @@
 
 package net.coobird.thumbnailator.resizers;
 
+import net.coobird.thumbnailator.builders.BufferedImageBuilder;
+
 import java.awt.AlphaComposite;
 import java.awt.Graphics2D;
 import java.awt.RenderingHints;
@@ -97,11 +99,11 @@ public void resize(BufferedImage srcImage, BufferedImage destImage)
 		}
 
 		// Temporary image used for in-place resizing of image.
-		BufferedImage tempImage = new BufferedImage(
+		BufferedImage tempImage = new BufferedImageBuilder(
 				currentWidth,
 				currentHeight,
 				destImage.getType()
-		);
+		).build();
 
 		Graphics2D g = createGraphics(tempImage);
 		g.setComposite(AlphaComposite.Src);

src/main/java/net/coobird/thumbnailator/util/BufferedImages.java

@@ -24,6 +24,8 @@
 
 package net.coobird.thumbnailator.util;
 
+import net.coobird.thumbnailator.builders.BufferedImageBuilder;
+
 import java.awt.Graphics;
 import java.awt.image.BufferedImage;
 
@@ -61,12 +63,11 @@ public static BufferedImage copy(BufferedImage img) {
 	public static BufferedImage copy(BufferedImage img, int imageType) {
 		int width = img.getWidth();
 		int height = img.getHeight();
-
-		BufferedImage newImage = new BufferedImage(width, height, imageType);
+
+		BufferedImage newImage = new BufferedImageBuilder(width, height, imageType).build();
+
 		Graphics g = newImage.createGraphics();
-
 		g.drawImage(img, 0, 0, null);
-
 		g.dispose();
 
 		return newImage;