imgresample.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

        else
#endif
            v_resample(output, owidth,
                       s->line_buf + (ring_y - NB_TAPS + 1) * owidth, owidth,
                       &s->v_filters[phase_y][0]);

        src_y += s->v_incr;

        output += owrap;
    }
}

ImgReSampleContext *img_resample_init(int owidth, int oheight,
                                      int iwidth, int iheight)
{
    return img_resample_full_init(owidth, oheight, iwidth, iheight,
            0, 0, 0, 0, 0, 0, 0, 0);
}

ImgReSampleContext *img_resample_full_init(int owidth, int oheight,
                                      int iwidth, int iheight,
                                      int topBand, int bottomBand,
        int leftBand, int rightBand,
        int padtop, int padbottom,
        int padleft, int padright)
{
    ImgReSampleContext *s;

    if (!owidth || !oheight || !iwidth || !iheight)
        return NULL;

    s = av_mallocz(sizeof(ImgReSampleContext));
    if (!s)
        return NULL;
    if((unsigned)owidth >= UINT_MAX / (LINE_BUF_HEIGHT + NB_TAPS))
        return NULL;
    s->line_buf = av_mallocz(owidth * (LINE_BUF_HEIGHT + NB_TAPS));
    if (!s->line_buf)
        goto fail;

    s->owidth = owidth;
    s->oheight = oheight;
    s->iwidth = iwidth;
    s->iheight = iheight;

    s->topBand = topBand;
    s->bottomBand = bottomBand;
    s->leftBand = leftBand;
    s->rightBand = rightBand;

    s->padtop = padtop;
    s->padbottom = padbottom;
    s->padleft = padleft;
    s->padright = padright;

    s->pad_owidth = owidth - (padleft + padright);
    s->pad_oheight = oheight - (padtop + padbottom);

    s->h_incr = ((iwidth - leftBand - rightBand) * POS_FRAC) / s->pad_owidth;
    s->v_incr = ((iheight - topBand - bottomBand) * POS_FRAC) / s->pad_oheight;

    av_build_filter(&s->h_filters[0][0], (float) s->pad_owidth  /
            (float) (iwidth - leftBand - rightBand), NB_TAPS, NB_PHASES, 1<<FILTER_BITS, 0);
    av_build_filter(&s->v_filters[0][0], (float) s->pad_oheight /
            (float) (iheight - topBand - bottomBand), NB_TAPS, NB_PHASES, 1<<FILTER_BITS, 0);

    return s;
fail:
    av_free(s);
    return NULL;
}

void img_resample(ImgReSampleContext *s,
                  AVPicture *output, const AVPicture *input)
{
    int i, shift;
    uint8_t* optr;

    for (i=0;i<3;i++) {
        shift = (i == 0) ? 0 : 1;

        optr = output->data[i] + (((output->linesize[i] *
                        s->padtop) + s->padleft) >> shift);

        component_resample(s, optr, output->linesize[i],
                s->pad_owidth >> shift, s->pad_oheight >> shift,
                input->data[i] + (input->linesize[i] *
                    (s->topBand >> shift)) + (s->leftBand >> shift),
                input->linesize[i], ((s->iwidth - s->leftBand -
                        s->rightBand) >> shift),
                           (s->iheight - s->topBand - s->bottomBand) >> shift);
    }
}

void img_resample_close(ImgReSampleContext *s)
{
    av_free(s->line_buf);
    av_free(s);
}

struct SwsContext *sws_getContext(int srcW, int srcH, int srcFormat,
                                  int dstW, int dstH, int dstFormat,
                                  int flags, SwsFilter *srcFilter,
                                  SwsFilter *dstFilter, double *param)
{
    struct SwsContext *ctx;

    ctx = av_malloc(sizeof(struct SwsContext));
    if (ctx)
        ctx->av_class = av_mallocz(sizeof(AVClass));
    if (!ctx || !ctx->av_class) {
        av_log(NULL, AV_LOG_ERROR, "Cannot allocate a resampling context!\n");

        return NULL;
    }

    if ((srcH != dstH) || (srcW != dstW)) {
        if ((srcFormat != PIX_FMT_YUV420P) || (dstFormat != PIX_FMT_YUV420P)) {
            av_log(NULL, AV_LOG_INFO, "PIX_FMT_YUV420P will be used as an intermediate format for rescaling\n");
        }
        ctx->resampling_ctx = img_resample_init(dstW, dstH, srcW, srcH);
    } else {
        ctx->resampling_ctx = av_malloc(sizeof(ImgReSampleContext));
        ctx->resampling_ctx->iheight = srcH;
        ctx->resampling_ctx->iwidth = srcW;
        ctx->resampling_ctx->oheight = dstH;
        ctx->resampling_ctx->owidth = dstW;
    }
    ctx->src_pix_fmt = srcFormat;
    ctx->dst_pix_fmt = dstFormat;

    return ctx;
}

void sws_freeContext(struct SwsContext *ctx)
{
    if (!ctx)
        return;
    if ((ctx->resampling_ctx->iwidth != ctx->resampling_ctx->owidth) ||
        (ctx->resampling_ctx->iheight != ctx->resampling_ctx->oheight)) {
        img_resample_close(ctx->resampling_ctx);
    } else {
        av_free(ctx->resampling_ctx);
    }
    av_free(ctx->av_class);
    av_free(ctx);
}


/**
 * Checks if context is valid or reallocs a new one instead.
 * If context is NULL, just calls sws_getContext() to get a new one.
 * Otherwise, checks if the parameters are the same already saved in context.
 * If that is the case, returns the current context.
 * Otherwise, frees context and gets a new one.
 *
 * Be warned that srcFilter, dstFilter are not checked, they are
 * asumed to remain valid.
 */
struct SwsContext *sws_getCachedContext(struct SwsContext *ctx,
                        int srcW, int srcH, int srcFormat,
                        int dstW, int dstH, int dstFormat, int flags,
                        SwsFilter *srcFilter, SwsFilter *dstFilter, double *param)
{
    if (ctx != NULL) {
        if ((ctx->resampling_ctx->iwidth != srcW) ||
                        (ctx->resampling_ctx->iheight != srcH) ||
                        (ctx->src_pix_fmt != srcFormat) ||
                        (ctx->resampling_ctx->owidth != dstW) ||
                        (ctx->resampling_ctx->oheight != dstH) ||
                        (ctx->dst_pix_fmt != dstFormat))
        {
            sws_freeContext(ctx);
            ctx = NULL;
        }
    }
    if (ctx == NULL) {
        return sws_getContext(srcW, srcH, srcFormat,
                        dstW, dstH, dstFormat, flags,
                        srcFilter, dstFilter, param);
    }
    return ctx;
}

int sws_scale(struct SwsContext *ctx, uint8_t* src[], int srcStride[],
              int srcSliceY, int srcSliceH, uint8_t* dst[], int dstStride[])
{
    AVPicture src_pict, dst_pict;
    int i, res = 0;
    AVPicture picture_format_temp;
    AVPicture picture_resample_temp, *formatted_picture, *resampled_picture;
    uint8_t *buf1 = NULL, *buf2 = NULL;
    enum PixelFormat current_pix_fmt;

    for (i = 0; i < 4; i++) {
        src_pict.data[i] = src[i];
        src_pict.linesize[i] = srcStride[i];
        dst_pict.data[i] = dst[i];
        dst_pict.linesize[i] = dstStride[i];
    }
    if ((ctx->resampling_ctx->iwidth != ctx->resampling_ctx->owidth) ||
        (ctx->resampling_ctx->iheight != ctx->resampling_ctx->oheight)) {
        /* We have to rescale the picture, but only YUV420P rescaling is supported... */

        if (ctx->src_pix_fmt != PIX_FMT_YUV420P) {
            int size;

            /* create temporary picture for rescaling input*/
            size = avpicture_get_size(PIX_FMT_YUV420P, ctx->resampling_ctx->iwidth, ctx->resampling_ctx->iheight);
            buf1 = av_malloc(size);
            if (!buf1) {
                res = -1;
                goto the_end;
            }
            formatted_picture = &picture_format_temp;
            avpicture_fill((AVPicture*)formatted_picture, buf1,
                           PIX_FMT_YUV420P, ctx->resampling_ctx->iwidth, ctx->resampling_ctx->iheight);

            if (img_convert((AVPicture*)formatted_picture, PIX_FMT_YUV420P,
                            &src_pict, ctx->src_pix_fmt,
                            ctx->resampling_ctx->iwidth, ctx->resampling_ctx->iheight) < 0) {

                av_log(NULL, AV_LOG_ERROR, "pixel format conversion not handled\n");
                res = -1;
                goto the_end;
            }
        } else {
            formatted_picture = &src_pict;
        }

        if (ctx->dst_pix_fmt != PIX_FMT_YUV420P) {
            int size;

            /* create temporary picture for rescaling output*/
            size = avpicture_get_size(PIX_FMT_YUV420P, ctx->resampling_ctx->owidth, ctx->resampling_ctx->oheight);
            buf2 = av_malloc(size);
            if (!buf2) {
                res = -1;
                goto the_end;
            }
            resampled_picture = &picture_resample_temp;
            avpicture_fill((AVPicture*)resampled_picture, buf2,
                           PIX_FMT_YUV420P, ctx->resampling_ctx->owidth, ctx->resampling_ctx->oheight);

        } else {
            resampled_picture = &dst_pict;
        }

        /* ...and finally rescale!!! */
        img_resample(ctx->resampling_ctx, resampled_picture, formatted_picture);
        current_pix_fmt = PIX_FMT_YUV420P;
    } else {
        resampled_picture = &src_pict;
        current_pix_fmt = ctx->src_pix_fmt;
    }

    if (current_pix_fmt != ctx->dst_pix_fmt) {
        if (img_convert(&dst_pict, ctx->dst_pix_fmt,
                        resampled_picture, current_pix_fmt,
                        ctx->resampling_ctx->owidth, ctx->resampling_ctx->oheight) < 0) {

            av_log(NULL, AV_LOG_ERROR, "pixel format conversion not handled\n");

            res = -1;
            goto the_end;
        }
    } else if (resampled_picture != &dst_pict) {
        av_picture_copy(&dst_pict, resampled_picture, current_pix_fmt,
                        ctx->resampling_ctx->owidth, ctx->resampling_ctx->oheight);
    }

the_end:
    av_free(buf1);
    av_free(buf2);
    return res;
}


#ifdef TEST
#include <stdio.h>
#undef exit

/* input */
#define XSIZE 256
#define YSIZE 256
uint8_t img[XSIZE * YSIZE];

/* output */
#define XSIZE1 512
#define YSIZE1 512
uint8_t img1[XSIZE1 * YSIZE1];
uint8_t img2[XSIZE1 * YSIZE1];

void save_pgm(const char *filename, uint8_t *img, int xsize, int ysize)
{
#undef fprintf
    FILE *f;
    f=fopen(filename,"w");
    fprintf(f,"P5\n%d %d\n%d\n", xsize, ysize, 255);
    fwrite(img,1, xsize * ysize,f);
    fclose(f);
#define fprintf please_use_av_log
}

static void dump_filter(int16_t *filter)
{
    int i, ph;

    for(ph=0;ph<NB_PHASES;ph++) {
        av_log(NULL, AV_LOG_INFO, "%2d: ", ph);
        for(i=0;i<NB_TAPS;i++) {
            av_log(NULL, AV_LOG_INFO, " %5.2f", filter[ph * NB_TAPS + i] / 256.0);
        }
        av_log(NULL, AV_LOG_INFO, "\n");
    }
}

#ifdef HAVE_MMX
int mm_flags;
#endif

int main(int argc, char **argv)
{
    int x, y, v, i, xsize, ysize;
    ImgReSampleContext *s;
    float fact, factors[] = { 1/2.0, 3.0/4.0, 1.0, 4.0/3.0, 16.0/9.0, 2.0 };
    char buf[256];

    /* build test image */
    for(y=0;y<YSIZE;y++) {
        for(x=0;x<XSIZE;x++) {
            if (x < XSIZE/2 && y < YSIZE/2) {
                if (x < XSIZE/4 && y < YSIZE/4) {
                    if ((x % 10) <= 6 &&
                        (y % 10) <= 6)
                        v = 0xff;
                    else
                        v = 0x00;
                } else if (x < XSIZE/4) {
                    if (x & 1)
                        v = 0xff;
                    else
                        v = 0;
                } else if (y < XSIZE/4) {
                    if (y & 1)
                        v = 0xff;
                    else
                        v = 0;
                } else {
                    if (y < YSIZE*3/8) {
                        if ((y+x) & 1)
                            v = 0xff;
                        else
                            v = 0;
                    } else {
                        if (((x+3) % 4) <= 1 &&
                            ((y+3) % 4) <= 1)
                            v = 0xff;
                        else
                            v = 0x00;
                    }
                }
            } else if (x < XSIZE/2) {
                v = ((x - (XSIZE/2)) * 255) / (XSIZE/2);
            } else if (y < XSIZE/2) {
                v = ((y - (XSIZE/2)) * 255) / (XSIZE/2);
            } else {
                v = ((x + y - XSIZE) * 255) / XSIZE;
            }
            img[(YSIZE - y) * XSIZE + (XSIZE - x)] = v;
        }
    }
    save_pgm("/tmp/in.pgm", img, XSIZE, YSIZE);
    for(i=0;i<sizeof(factors)/sizeof(float);i++) {
        fact = factors[i];
        xsize = (int)(XSIZE * fact);
        ysize = (int)((YSIZE - 100) * fact);
        s = img_resample_full_init(xsize, ysize, XSIZE, YSIZE, 50 ,50, 0, 0, 0, 0, 0, 0);
        av_log(NULL, AV_LOG_INFO, "Factor=%0.2f\n", fact);
        dump_filter(&s->h_filters[0][0]);
        component_resample(s, img1, xsize, xsize, ysize,
                           img + 50 * XSIZE, XSIZE, XSIZE, YSIZE - 100);
        img_resample_close(s);

        snprintf(buf, sizeof(buf), "/tmp/out%d.pgm", i);
        save_pgm(buf, img1, xsize, ysize);
    }

    /* mmx test */
#ifdef HAVE_MMX
    av_log(NULL, AV_LOG_INFO, "MMX test\n");
    fact = 0.72;
    xsize = (int)(XSIZE * fact);
    ysize = (int)(YSIZE * fact);
    mm_flags = MM_MMX;
    s = img_resample_init(xsize, ysize, XSIZE, YSIZE);
    component_resample(s, img1, xsize, xsize, ysize,
                       img, XSIZE, XSIZE, YSIZE);

    mm_flags = 0;
    s = img_resample_init(xsize, ysize, XSIZE, YSIZE);
    component_resample(s, img2, xsize, xsize, ysize,
                       img, XSIZE, XSIZE, YSIZE);
    if (memcmp(img1, img2, xsize * ysize) != 0) {
        av_log(NULL, AV_LOG_ERROR, "mmx error\n");
        exit(1);
    }
    av_log(NULL, AV_LOG_INFO, "MMX OK\n");
#endif /* HAVE_MMX */
    return 0;
}

#endif /* TEST */