[FFmpeg-devel] [PATCH] Add FITS Decoder

[Michael Niedermayer]

On Thu, Jun 08, 2017 at 10:34:15PM +0530, Paras Chadha wrote:
> It supports all 2-d images alongwith bzero, bscale and blank keywords.
> RGBA images are supported as NAXIS3 = 3 or 4 i.e. Planes in RGBA order. Also CTYPE = 'RGB ' should be present.
> It currently does not support XTENSION keyword.
> 
> Signed-off-by: Paras Chadha <paraschadha18 at gmail.com>
> ---
>  Changelog                |   1 +
>  doc/general.texi         |   2 +
>  libavcodec/Makefile      |   1 +
>  libavcodec/allcodecs.c   |   1 +
>  libavcodec/avcodec.h     |   1 +
>  libavcodec/codec_desc.c  |   8 +
>  libavcodec/fitsdec.c     | 527 +++++++++++++++++++++++++++++++++++++++++++++++
>  libavcodec/version.h     |   4 +-
>  libavformat/Makefile     |   1 +
>  libavformat/allformats.c |   1 +
>  libavformat/img2.c       |   1 +
>  libavformat/img2dec.c    |  10 +
>  12 files changed, 556 insertions(+), 2 deletions(-)
>  create mode 100644 libavcodec/fitsdec.c
[...]
> +/**
> + * function reads the fits header and stores the values in fits_header pointed by header
> + * @param avctx - AVCodec context
> + * @param ptr - pointer to pointer to the data
> + * @param header - pointer to the fits_header
> + * @param end - pointer to end of packet
> + * @return 1, if calculated successfully, otherwise AVERROR_INVALIDDATA
> + */
> +static int fits_read_header(AVCodecContext *avctx, const uint8_t **ptr, fits_header * header, const uint8_t * end)
> +{
> +    const uint8_t *ptr8 = *ptr;
> +    int lines_read = 0, i, dim_no, t, data_min_found = 0, data_max_found = 0, ret;
> +    uint64_t size=1;
> +    char str_val[80];
> +    double d;
> +
> +    header->blank = 0;
> +    header->bscale = 1.0;
> +    header->bzero = 0;
> +    header->rgb = 0;
> +
> +    if (end - ptr8 < 80)
> +        return AVERROR_INVALIDDATA;
> +
> +    if (sscanf(ptr8, "SIMPLE = %c", &header->simple) != 1) {
> +        av_log(avctx, AV_LOG_ERROR, "missing SIMPLE keyword\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    if (header->simple == 'F')
> +        av_log(avctx, AV_LOG_WARNING, "not a standard FITS file\n");
> +    else if (header->simple != 'T') {
> +        av_log(avctx, AV_LOG_ERROR, "invalid SIMPLE value, SIMPLE = %c\n", header->simple);
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    ptr8 += 80;
> +    lines_read++;
> +
> +    if (end - ptr8 < 80)
> +        return AVERROR_INVALIDDATA;
> +
> +    if (sscanf(ptr8, "BITPIX = %d", &header->bitpix) != 1) {
> +        av_log(avctx, AV_LOG_ERROR, "missing BITPIX keyword\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    size = abs(header->bitpix) / 8;
> +    ptr8 += 80;
> +    lines_read++;
> +
> +    if (end - ptr8 < 80)
> +        return AVERROR_INVALIDDATA;
> +
> +    if (sscanf(ptr8, "NAXIS = %d", &header->naxis) != 1) {
> +        av_log(avctx, AV_LOG_ERROR, "missing NAXIS keyword\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    if (header->naxis == 0) {
> +        av_log(avctx, AV_LOG_ERROR, "No image data found, NAXIS = %d\n", header->naxis);
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    if (header->naxis != 2 && header->naxis != 3) {
> +        av_log(avctx, AV_LOG_ERROR, "unsupported number of dimensions, NAXIS = %d\n", header->naxis);
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    ptr8 += 80;
> +    lines_read++;
> +
> +    for (i = 0; i < header->naxis; i++) {
> +        if (end - ptr8 < 80)
> +            return AVERROR_INVALIDDATA;
> +
> +        if (sscanf(ptr8, "NAXIS%d = %d", &dim_no, &header->naxisn[i]) != 2 || dim_no != i+1) {
> +            av_log(avctx, AV_LOG_ERROR, "missing NAXIS%d keyword\n", i+1);
> +            return AVERROR_INVALIDDATA;
> +        }
> +
> +        size *= header->naxisn[i];
> +        ptr8 += 80;
> +        lines_read++;
> +    }
> +
> +    if (end - ptr8 < 80)
> +            return AVERROR_INVALIDDATA;
> +
> +    while (strncmp(ptr8, "END", 3)) {
> +        if (sscanf(ptr8, "BLANK = %d", &t) == 1)
> +            header->blank = t;
> +        else if (sscanf(ptr8, "BSCALE = %lf", &d) == 1)
> +            header->bscale = d;
> +        else if (sscanf(ptr8, "BZERO = %lf", &d) == 1)
> +            header->bzero = d;
> +        else if (sscanf(ptr8, "DATAMAX = %lf", &d) == 1) {
> +            data_max_found = 1;
> +            header->data_max = d;
> +        }
> +        else if (sscanf(ptr8, "DATAMIN = %lf", &d) == 1) {
> +            data_min_found = 1;
> +            header->data_min = d;
> +        }

> +        else if (sscanf(ptr8, "CTYPE3 = '%s '", str_val) == 1) {

what prevents a buffer overflow here ?

[...]
> +
> +static int fits_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
> +{
> +    AVFrame *p=data;
> +    const uint8_t *ptr8 = avpkt->data, *end;
> +    int16_t t16;
> +    int32_t t32;
> +    int64_t t64;
> +    float   tflt;
> +    double  tdbl;
> +    int ret, i, j;
> +    uint8_t *dst8;
> +    uint16_t *dst16;
> +    uint32_t *dst32;
> +    uint64_t *dst64, size, r, g, b, a, t;
> +    fits_header header;
> +
> +    end = ptr8 + avpkt->size;

> +    if ((ret = fits_read_header(avctx, &ptr8, &header, end) < 0))

wrongly placed ()



[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Take away the freedom of one citizen and you will be jailed, take away
the freedom of all citizens and you will be congratulated by your peers
in Parliament.
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