if(buf_size < avpicture_get_size(avctx->pix_fmt, avctx->width, avctx->height) + 200){ av_log(avctx, AV_LOG_ERROR, "encoded frame too large\n"); return -1; }
static int pam_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data){    PNMContext *s = avctx->priv_data;    AVFrame *pict = data;    AVFrame * const p= (AVFrame*)&s->picture;    int i, h, w, n, linesize, depth, maxval;    const char *tuple_type;    uint8_t *ptr;    *p = *pict;    p->pict_type= FF_I_TYPE;    p->key_frame= 1;        s->bytestream_start=    s->bytestream= outbuf;    s->bytestream_end= outbuf+buf_size;    h = avctx->height;    w = avctx->width;    switch(avctx->pix_fmt) {    case PIX_FMT_MONOWHITE:        n = (w + 7) >> 3;        depth = 1;        maxval = 1;        tuple_type = "BLACKANDWHITE";        break;    case PIX_FMT_GRAY8:        n = w;        depth = 1;        maxval = 255;        tuple_type = "GRAYSCALE";        break;    case PIX_FMT_RGB24:        n = w * 3;        depth = 3;        maxval = 255;        tuple_type = "RGB";        break;    case PIX_FMT_RGBA32:        n = w * 4;        depth = 4;        maxval = 255;        tuple_type = "RGB_ALPHA";        break;    default:        return -1;    }    snprintf(s->bytestream, s->bytestream_end - s->bytestream,              "P7\nWIDTH %d\nHEIGHT %d\nDEPTH %d\nMAXVAL %d\nTUPLETYPE %s\nENDHDR\n",             w, h, depth, maxval, tuple_type);    s->bytestream += strlen(s->bytestream);        ptr = p->data[0];    linesize = p->linesize[0];        if (avctx->pix_fmt == PIX_FMT_RGBA32) {        int j;        unsigned int v;        for(i=0;i<h;i++) {            for(j=0;j<w;j++) {                v = ((uint32_t *)ptr)[j];                *s->bytestream++ = v >> 16;                *s->bytestream++ = v >> 8;                *s->bytestream++ = v;                *s->bytestream++ = v >> 24;            }            ptr += linesize;        }    } else {        for(i=0;i<h;i++) {            memcpy(s->bytestream, ptr, n);            s->bytestream += n;            ptr += linesize;        }    }    return s->bytestream - s->bytestream_start;}