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Add Image.alpha_composite

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commit e414c660709d233df3a2dfbe69cf0500297d6c47 1 parent 4a10a36
@twpayne twpayne authored
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15 PIL/Image.py
@@ -1981,6 +1981,21 @@ def open(fp, mode="r"):
# Image processing.
##
+# Alpha composites im2 over im1.
+#
+# @param im1 The first image.
+# @param im2 The second image. Must have the same mode and size as
+# the first image.
+# @return An Image object.
+
+def alpha_composite(im1, im2):
+ "Alpha composite im2 over im1."
+
+ im1.load()
+ im2.load()
+ return im1._new(core.alpha_composite(im1.im, im2.im))
+
+##
# Creates a new image by interpolating between two input images, using
# a constant alpha.
#
View
15 _imaging.c
@@ -694,6 +694,20 @@ _open_ppm(PyObject* self, PyObject* args)
return PyImagingNew(ImagingOpenPPM(filename));
}
+static PyObject*
+_alpha_composite(ImagingObject* self, PyObject* args)
+{
+ ImagingObject* imagep1;
+ ImagingObject* imagep2;
+
+ if (!PyArg_ParseTuple(args, "O!O!",
+ &Imaging_Type, &imagep1,
+ &Imaging_Type, &imagep2))
+ return NULL;
+
+ return PyImagingNew(ImagingAlphaComposite(imagep1->image, imagep2->image));
+}
+
static PyObject*
_blend(ImagingObject* self, PyObject* args)
{
@@ -3152,6 +3166,7 @@ extern PyObject* PyImaging_MapBuffer(PyObject* self, PyObject* args);
static PyMethodDef functions[] = {
/* Object factories */
+ {"alpha_composite", (PyCFunction)_alpha_composite, 1},
{"blend", (PyCFunction)_blend, 1},
{"fill", (PyCFunction)_fill, 1},
{"new", (PyCFunction)_new, 1},
View
94 libImaging/AlphaComposite.c
@@ -0,0 +1,94 @@
+/*
+ * The Python Imaging Library
+ * $Id$
+ *
+ * Alpha composite imSrc over imDst.
+ * http://en.wikipedia.org/wiki/Alpha_compositing
+ *
+ * See the README file for details on usage and redistribution.
+ */
+
+
+#include "Imaging.h"
+
+
+Imaging
+ImagingAlphaComposite(Imaging imDst, Imaging imSrc)
+{
+ Imaging imOut;
+ int x, y;
+ float dstR, dstG, dstB, dstA;
+ float srcR, srcG, srcB, srcA;
+ float outR, outG, outB, outA;
+
+ /* Check arguments */
+ if (!imDst || !imSrc ||
+ strcmp(imDst->mode, "RGBA") ||
+ imDst->type != IMAGING_TYPE_UINT8 ||
+ imDst->bands != 4)
+ return ImagingError_ModeError();
+ if (strcmp(imDst->mode, imSrc->mode) ||
+ imDst->type != imSrc->type ||
+ imDst->bands != imSrc->bands ||
+ imDst->xsize != imSrc->xsize ||
+ imDst->ysize != imSrc->ysize)
+ return ImagingError_Mismatch();
+
+ imOut = ImagingNew(imDst->mode, imDst->xsize, imDst->ysize);
+ if (!imOut)
+ return NULL;
+
+ ImagingCopyInfo(imOut, imDst);
+
+ for (y = 0; y < imDst->ysize; y++) {
+
+ UINT8* dst = (UINT8*) imDst->image[y];
+ UINT8* src = (UINT8*) imSrc->image[y];
+ UINT8* out = (UINT8*) imOut->image[y];
+
+ for (x = 0; x < imDst->linesize; x += 4) {
+
+ dstR = dst[x + 0] / 255.0;
+ dstG = dst[x + 1] / 255.0;
+ dstB = dst[x + 2] / 255.0;
+ dstA = dst[x + 3] / 255.0;
+
+ srcR = src[x + 0] / 255.0;
+ srcG = src[x + 1] / 255.0;
+ srcB = src[x + 2] / 255.0;
+ srcA = src[x + 3] / 255.0;
+
+ if (dstA == 1.0) {
+ outR = srcR * srcA + dstR * (1.0 - srcA);
+ outG = srcG * srcA + dstG * (1.0 - srcA);
+ outB = srcB * srcA + dstB * (1.0 - srcA);
+ outA = 1.0;
+ } else if (srcA == 0.0) {
+ outR = dstR;
+ outG = dstG;
+ outB = dstB;
+ outA = dstA;
+ } else {
+ outA = srcA + dstA * (1.0 - srcA);
+ if (outA == 0.0) {
+ outR = 0.0;
+ outG = 0.0;
+ outB = 0.0;
+ } else {
+ outR = (srcR * srcA + dstR * dstA * (1.0 - srcA)) / outA;
+ outG = (srcG * srcA + dstG * dstA * (1.0 - srcA)) / outA;
+ outB = (srcB * srcA + dstB * dstA * (1.0 - srcA)) / outA;
+ }
+ }
+
+ out[x + 0] = (UINT8) (255.0 * outR);
+ out[x + 1] = (UINT8) (255.0 * outG);
+ out[x + 2] = (UINT8) (255.0 * outB);
+ out[x + 3] = (UINT8) (255.0 * outA);
+
+ }
+
+ }
+
+ return imOut;
+}
View
1  libImaging/Imaging.h
@@ -239,6 +239,7 @@ typedef int (*ImagingTransformFilter)(void* out, Imaging im,
/* Image Manipulation Methods */
/* -------------------------- */
+extern Imaging ImagingAlphaComposite(Imaging imIn1, Imaging imIn2);
extern Imaging ImagingBlend(Imaging imIn1, Imaging imIn2, float alpha);
extern Imaging ImagingCopy(Imaging im);
extern Imaging ImagingConvert(Imaging im, const char* mode, ImagingPalette palette, int dither);
View
4 setup.py
@@ -15,8 +15,8 @@
)
_LIB_IMAGING = (
- "Access", "Antialias", "Bands", "BitDecode", "Blend", "Chops",
- "Convert", "ConvertYCbCr", "Copy", "Crc32", "Crop", "Dib", "Draw",
+ "Access", "AlphaComposite", "Antialias", "Bands", "BitDecode", "Blend",
+ "Chops", "Convert", "ConvertYCbCr", "Copy", "Crc32", "Crop", "Dib", "Draw",
"Effects", "EpsEncode", "File", "Fill", "Filter", "FliDecode",
"Geometry", "GetBBox", "GifDecode", "GifEncode", "HexDecode",
"Histo", "JpegDecode", "JpegEncode", "LzwDecode", "Matrix",
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