Pillow

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/*
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 * The Python Imaging Library
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 * $Id$
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 *
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 * colour and luminance matrix transforms
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 *
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 * history:
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 * 1996-05-18 fl:   created (brute force implementation)
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 *
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 * Copyright (c) Fredrik Lundh 1996.
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 * Copyright (c) Secret Labs AB 1997.
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 *
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 * See the README file for information on usage and redistribution.
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 */
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#include "Imaging.h"
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#define CLIPF(v) ((v <= 0.0) ? 0 : (v >= 255.0F) ? 255 : (UINT8)v)
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Imaging
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ImagingConvertMatrix(Imaging im, const char *mode, float m[]) {
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    Imaging imOut;
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    int x, y;
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    ImagingSectionCookie cookie;
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    /* Assume there's enough data in the buffer */
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    if (!im || im->bands != 3) {
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        return (Imaging)ImagingError_ModeError();
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    }
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    if (strcmp(mode, "L") == 0) {
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        imOut = ImagingNewDirty("L", im->xsize, im->ysize);
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        if (!imOut) {
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            return NULL;
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        }
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        ImagingSectionEnter(&cookie);
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        for (y = 0; y < im->ysize; y++) {
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            UINT8 *in = (UINT8 *)im->image[y];
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            UINT8 *out = (UINT8 *)imOut->image[y];
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            for (x = 0; x < im->xsize; x++) {
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                float v = m[0] * in[0] + m[1] * in[1] + m[2] * in[2] + m[3] + 0.5;
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                out[x] = CLIPF(v);
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                in += 4;
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            }
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        }
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        ImagingSectionLeave(&cookie);
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    } else if (strlen(mode) == 3) {
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        imOut = ImagingNewDirty(mode, im->xsize, im->ysize);
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        if (!imOut) {
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            return NULL;
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        }
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        for (y = 0; y < im->ysize; y++) {
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            UINT8 *in = (UINT8 *)im->image[y];
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            UINT8 *out = (UINT8 *)imOut->image[y];
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            ImagingSectionEnter(&cookie);
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            for (x = 0; x < im->xsize; x++) {
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                float v0 = m[0] * in[0] + m[1] * in[1] + m[2] * in[2] + m[3] + 0.5;
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                float v1 = m[4] * in[0] + m[5] * in[1] + m[6] * in[2] + m[7] + 0.5;
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                float v2 = m[8] * in[0] + m[9] * in[1] + m[10] * in[2] + m[11] + 0.5;
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                out[0] = CLIPF(v0);
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                out[1] = CLIPF(v1);
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                out[2] = CLIPF(v2);
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                in += 4;
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                out += 4;
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            }
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            ImagingSectionLeave(&cookie);
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        }
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    } else {
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        return (Imaging)ImagingError_ModeError();
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    }
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    return imOut;
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}
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