1 files changed, 79 insertions, 0 deletions
diff --git a/Imaging/libImaging/Blend.c b/Imaging/libImaging/Blend.c
new file mode 100644
index 0000000..4d8db66
--- /dev/null
+++ b/Imaging/libImaging/Blend.c
@@ -0,0 +1,79 @@
+/* 
+ * The Python Imaging Library
+ * $Id: Blend.c 2134 2004-10-06 08:55:20Z fredrik $
+ *
+ * interpolate between two existing images
+ *
+ * history:
+ * 96-03-20 fl	Created
+ * 96-05-18 fl	Simplified blend expression
+ * 96-10-05 fl	Fixed expression bug, special case for interpolation
+ *
+ * Copyright (c) Fredrik Lundh 1996.
+ * Copyright (c) Secret Labs AB 1997.
+ *
+ * See the README file for details on usage and redistribution.
+ */
+
+
+#include "Imaging.h"
+
+
+Imaging
+ImagingBlend(Imaging imIn1, Imaging imIn2, float alpha)
+{
+    Imaging imOut;
+    int x, y;
+
+    /* Check arguments */
+    if (!imIn1 || !imIn2 || imIn1->type != IMAGING_TYPE_UINT8)
+	return ImagingError_ModeError();
+    if (imIn1->type  != imIn2->type  ||
+	imIn1->bands != imIn2->bands ||
+	imIn1->xsize != imIn2->xsize ||
+	imIn1->ysize != imIn2->ysize)
+	return ImagingError_Mismatch();
+
+    /* Shortcuts */
+    if (alpha == 0.0)
+	return ImagingCopy(imIn1);
+    else if (alpha == 1.0)
+	return ImagingCopy(imIn2);
+
+    imOut = ImagingNew(imIn1->mode, imIn1->xsize, imIn1->ysize);
+    if (!imOut)
+	return NULL;
+
+    ImagingCopyInfo(imOut, imIn1);
+
+    if (alpha >= 0 && alpha <= 1.0) {
+	/* Interpolate between bands */
+	for (y = 0; y < imIn1->ysize; y++) {
+	    UINT8* in1 = (UINT8*) imIn1->image[y];
+	    UINT8* in2 = (UINT8*) imIn2->image[y];
+	    UINT8* out = (UINT8*) imOut->image[y];
+	    for (x = 0; x < imIn1->linesize; x++)
+		out[x] = (UINT8)
+		    ((int) in1[x] + alpha * ((int) in2[x] - (int) in1[x]));
+	}
+    } else {
+	/* Extrapolation; must make sure to clip resulting values */
+	for (y = 0; y < imIn1->ysize; y++) {
+	    UINT8* in1 = (UINT8*) imIn1->image[y];
+	    UINT8* in2 = (UINT8*) imIn2->image[y];
+	    UINT8* out = (UINT8*) imOut->image[y];
+	    for (x = 0; x < imIn1->linesize; x++) {
+		float temp =
+		    ((int) in1[x] + alpha * ((int) in2[x] - (int) in1[x]));
+		if (temp <= 0.0)
+		    out[x] = 0;
+		else if (temp >= 255.0)
+		    out[x] = 255;
+		else
+		    out[x] = (UINT8) temp;
+	    }
+	}
+    }
+
+    return imOut;
+}