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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 * encoder for PCX data
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 *
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 * history:
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 * 99-02-07 fl  created
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 *
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 * Copyright (c) Fredrik Lundh 1999.
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 * Copyright (c) Secret Labs AB 1999.
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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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enum { INIT, FETCH, ENCODE };
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/* we're reusing "ystep" to store the last value */
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#define LAST ystep
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int
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ImagingPcxEncode(Imaging im, ImagingCodecState state, UINT8 *buf, int bytes) {
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    UINT8 *ptr;
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    int this;
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    int bytes_per_line = 0;
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    int padding = 0;
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    int stride = 0;
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    int bpp = 0;
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    int planes = 1;
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    int i;
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    ptr = buf;
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    if (!state->state) {
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        /* sanity check */
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        if (state->xsize <= 0 || state->ysize <= 0) {
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            state->errcode = IMAGING_CODEC_END;
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            return 0;
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        }
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        state->state = FETCH;
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    }
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    bpp = state->bits;
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    if (state->bits == 24) {
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        planes = 3;
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        bpp = 8;
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    }
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    bytes_per_line = (state->xsize * bpp + 7) / 8;
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    /* The stride here needs to be kept in sync with the version in
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       PcxImagePlugin.py. If it's not, the header and the body of the
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       image will be out of sync and bad things will happen on decode.
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    */
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    stride = bytes_per_line + (bytes_per_line % 2);
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    padding = stride - bytes_per_line;
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    for (;;) {
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        switch (state->state) {
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            case FETCH:
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                /* get a line of data */
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                if (state->y >= state->ysize) {
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                    state->errcode = IMAGING_CODEC_END;
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                    return ptr - buf;
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                }
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                state->shuffle(
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                    state->buffer,
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                    (UINT8 *)im->image[state->y + state->yoff] +
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                        state->xoff * im->pixelsize,
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                    state->xsize
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                );
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                state->y += 1;
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                state->count = 1;
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                state->LAST = state->buffer[0];
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                state->x = 1;
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                state->state = ENCODE;
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                /* fall through */
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            case ENCODE:
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                /* compress this line */
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                /* when we arrive here, "count" contains the number of
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                   bytes having the value of "LAST" that we've already
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                   seen */
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                do {
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                    /* If we're encoding an odd width file, and we've
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                       got more than one plane, we need to pad each
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                       color row with padding bytes at the end. Since
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                       The pixels are stored RRRRRGGGGGBBBBB, so we need
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                       to have the padding be RRRRRPGGGGGPBBBBBP. Hence
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                       the double loop
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                    */
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                    while (state->x % bytes_per_line) {
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                        if (state->count == 63) {
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                            /* this run is full; flush it */
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                            if (bytes < 2) {
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                                return ptr - buf;
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                            }
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                            ptr[0] = 0xff;
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                            ptr[1] = state->LAST;
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                            ptr += 2;
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                            bytes -= 2;
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                            state->count = 0;
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                        }
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                        this = state->buffer[state->x];
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                        if (this == state->LAST) {
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                            /* extend the current run */
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                            state->x += 1;
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                            state->count += 1;
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                        } else {
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                            /* start a new run */
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                            if (state->count == 1 && (state->LAST < 0xc0)) {
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                                if (bytes < 1) {
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                                    return ptr - buf;
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                                }
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                                ptr[0] = state->LAST;
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                                ptr += 1;
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                                bytes -= 1;
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                            } else {
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                                if (state->count > 0) {
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                                    if (bytes < 2) {
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                                        return ptr - buf;
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                                    }
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                                    ptr[0] = 0xc0 | state->count;
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                                    ptr[1] = state->LAST;
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                                    ptr += 2;
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                                    bytes -= 2;
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                                }
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                            }
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                            state->LAST = this;
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                            state->count = 1;
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                            state->x += 1;
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                        }
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                    }
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                    /* end of line; flush the current run */
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                    if (state->count == 1 && (state->LAST < 0xc0)) {
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                        if (bytes < 1 + padding) {
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                            return ptr - buf;
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                        }
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                        ptr[0] = state->LAST;
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                        ptr += 1;
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                        bytes -= 1;
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                    } else {
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                        if (state->count > 0) {
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                            if (bytes < 2 + padding) {
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                                return ptr - buf;
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                            }
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                            ptr[0] = 0xc0 | state->count;
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                            ptr[1] = state->LAST;
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                            ptr += 2;
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                            bytes -= 2;
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                        }
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                    }
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                    /* add the padding */
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                    for (i = 0; i < padding; i++) {
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                        ptr[0] = 0;
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                        ptr += 1;
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                        bytes -= 1;
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                    }
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                    /* reset for the next color plane. */
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                    if (state->x < planes * bytes_per_line) {
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                        state->count = 1;
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                        state->LAST = state->buffer[state->x];
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                        state->x += 1;
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                    }
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                } while (state->x < planes * bytes_per_line);
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                /* read next line */
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                state->state = FETCH;
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                break;
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        }
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    }
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}
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