#ifndef SkDistanceFieldGen_DEFINED
#define SkDistanceFieldGen_DEFINED
+#include "SkTypes.h"
+
+// the max magnitude for the distance field
+// distance values are limited to the range [-SK_DistanceFieldMagnitude, SK_DistanceFieldMagnitude)
+#define SK_DistanceFieldMagnitude 4
+// we need to pad around the original glyph to allow our maximum distance of
+// SK_DistanceFieldMagnitude texels away from any edge
+#define SK_DistanceFieldPad 4
+// the rect we render with is inset from the distance field glyph size to allow for bilerp
+#define SK_DistanceFieldInset 2
+
+// for the fragment shader
+// The distance field is constructed as unsigned char values, so that the zero value is at 128,
+// and the range is [-4, 4 - 1/255). Hence our multiplier is 8 - 1/32 and zero threshold is 128/255.
+#define SK_DistanceFieldMultiplier "7.96875"
+#define SK_DistanceFieldThreshold "0.50196078431"
+
/** Given 8-bit mask data, generate the associated distance field
* @param distanceField The distance field to be generated. Should already be allocated
- * by the client with the padding below.
+ * by the client with the padding above.
* @param image 8-bit mask we're using to generate the distance field.
- * @param w Width of the image.
- * @param h Height of the image.
- * @param distanceMagnitude Largest possible absolute value for the distance. The distance field
- * will be padded to w + 2*distanceMagnitude, h + 2*distanceMagnitude.
+ * @param w Width of the original image.
+ * @param h Height of the original image.
+ * @param rowBytes Size of each row in the image, in bytes
+ */
+bool SkGenerateDistanceFieldFromA8Image(unsigned char* distanceField,
+ const unsigned char* image,
+ int w, int h, int rowBytes);
+
+/** Given 1-bit mask data, generate the associated distance field
+
+ * @param distanceField The distance field to be generated. Should already be allocated
+ * by the client with the padding above.
+ * @param image 1-bit mask we're using to generate the distance field.
+ * @param w Width of the original image.
+ * @param h Height of the original image.
+ * @param rowBytes Size of each row in the image, in bytes
+ */
+bool SkGenerateDistanceFieldFromBWImage(unsigned char* distanceField,
+ const unsigned char* image,
+ int w, int h, int rowBytes);
+
+/** Given width and height of original image, return size (in bytes) of distance field
+ * @param w Width of the original image.
+ * @param h Height of the original image.
*/
-bool SkGenerateDistanceFieldFromImage(unsigned char* distanceField,
- const unsigned char* image,
- int w, int h,
- int distanceMagnitude);
+inline size_t SkComputeDistanceFieldSize(int w, int h) {
+ return (w + 2*SK_DistanceFieldPad) * (h + 2*SK_DistanceFieldPad) * sizeof(unsigned char);
+}
#endif