Remove padding during scaling

YahooArchive · May 23, 2015 · 334c55e · 334c55e
1 parent dbd94de
commit 334c55e
Showing 1 changed file with 55 additions and 8 deletions.
diff --git a/lib/png/utils/scale.js b/lib/png/utils/scale.js
@@ -104,7 +104,8 @@ scale.scaleUp = function (input, output, spreadFn, isColor, hasAlphaChannel, isI
 		bytes = [],
 		bytesNeeded,
 		method,
-		increment = 1;
+		increment = 1,
+		currentBytes;
 
 	if (isIndexedColor) {
 		bytesNeeded = 1;
@@ -146,7 +147,8 @@ scale.scaleUp = function (input, output, spreadFn, isColor, hasAlphaChannel, isI
 		spreadFn(value, bytes);
 
 		while (bytes.length >= bytesNeeded) {
-			this[method](output, bytes.splice(0, bytesNeeded));
+			currentBytes = bytes.splice(0, bytesNeeded);
+			this[method](output, currentBytes);
 		}
 	}
 };
@@ -161,12 +163,15 @@ scale.scaleUp = function (input, output, spreadFn, isColor, hasAlphaChannel, isI
  * @param {boolean} isColor Is data in color?
  * @param {boolean} hasAlphaChannel Does  data have an alpha-channel?
  * @param {boolean} isIndexedColor Is image indexed on a palette?
+ * @param {number} paddingAt Defines the position of padding within each scanline
  */
-scale.scale1to8bit = function (input, output, isColor, hasAlphaChannel, isIndexedColor) {
+scale.scale1to8bit = function (input, output, isColor, hasAlphaChannel, isIndexedColor, paddingAt) {
 
-	var scaleFactor = isIndexedColor ? 1 : 255; // 255 / 1
+	var scaleFactor = isIndexedColor ? 1 : 255, // 255 / 1
+		byteCounter = 0;
 
 	this.scaleUp(input, output, function (value, bytes) {
+
 		bytes.push(((value >> 7) & 1) * scaleFactor);
 		bytes.push(((value >> 6) & 1) * scaleFactor);
 		bytes.push(((value >> 5) & 1) * scaleFactor);
@@ -175,6 +180,18 @@ scale.scale1to8bit = function (input, output, isColor, hasAlphaChannel, isIndexe
 		bytes.push(((value >> 2) & 1) * scaleFactor);
 		bytes.push(((value >> 1) & 1) * scaleFactor);
 		bytes.push((value & 1) * scaleFactor);
+
+		// Make sure that padding is removed
+		if (paddingAt) {
+			byteCounter += 8;
+			if (byteCounter >= paddingAt) {
+				if (byteCounter > paddingAt) {
+					bytes.splice(-(byteCounter - paddingAt));
+				}
+				byteCounter = 0;
+			}
+		}
+
 	}, isColor, hasAlphaChannel, isIndexedColor);
 };
 
@@ -188,16 +205,31 @@ scale.scale1to8bit = function (input, output, isColor, hasAlphaChannel, isIndexe
  * @param {boolean} isColor Is data in color?
  * @param {boolean} hasAlphaChannel Does  data have an alpha-channel?
  * @param {boolean} isIndexedColor Is image indexed on a palette?
+ * @param {number} paddingAt Defines the position of padding within each scanline
  */
-scale.scale2to8bit = function (input, output, isColor, hasAlphaChannel, isIndexedColor) {
+scale.scale2to8bit = function (input, output, isColor, hasAlphaChannel, isIndexedColor, paddingAt) {
 
-	var scaleFactor = isIndexedColor ? 1 : 255 / 3;
+	var scaleFactor = isIndexedColor ? 1 : 255 / 3,
+		byteCounter = 0;
 
 	this.scaleUp(input, output, function (value, bytes) {
+
 		bytes.push(((value >> 6) & 3) * scaleFactor);
 		bytes.push(((value >> 4) & 3) * scaleFactor);
 		bytes.push(((value >> 2) & 3) * scaleFactor);
 		bytes.push((value & 3) * scaleFactor);
+
+		// Make sure that padding is removed
+		if (paddingAt) {
+			byteCounter += 4;
+			if (byteCounter >= paddingAt) {
+				if (byteCounter > paddingAt) {
+					bytes.splice(-(byteCounter - paddingAt));
+				}
+				byteCounter = 0;
+			}
+		}
+
 	}, isColor, hasAlphaChannel, isIndexedColor);
 };
 
@@ -211,14 +243,29 @@ scale.scale2to8bit = function (input, output, isColor, hasAlphaChannel, isIndexe
  * @param {boolean} isColor Is data in color?
  * @param {boolean} hasAlphaChannel Does  data have an alpha-channel?
  * @param {boolean} isIndexedColor Is image indexed on a palette?
+ * @param {number} paddingAt Defines the position of padding within each scanline
  */
-scale.scale4to8bit = function (input, output, isColor, hasAlphaChannel, isIndexedColor) {
+scale.scale4to8bit = function (input, output, isColor, hasAlphaChannel, isIndexedColor, paddingAt) {
 
-	var scaleFactor = isIndexedColor ? 1 : 255 / 15;
+	var scaleFactor = isIndexedColor ? 1 : 255 / 15,
+		byteCounter = 0;
 
 	this.scaleUp(input, output, function (value, bytes) {
+
 		bytes.push(((value >> 4) & 15) * scaleFactor);
 		bytes.push((value & 15) * scaleFactor);
+
+		// Make sure that padding is removed
+		if (paddingAt) {
+			byteCounter += 2;
+			if (byteCounter >= paddingAt) {
+				if (byteCounter > paddingAt) {
+					bytes.splice(-(byteCounter - paddingAt));
+				}
+				byteCounter = 0;
+			}
+		}
+
 	}, isColor, hasAlphaChannel, isIndexedColor);
 };