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Add support for grayscale images with arbitrary maxvals.

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The image data is rescaled to the nearest pix_fmt it will fit in (gray8 or
gray16). Conversion is done inside the codec in order to avoid the need
for 14 (or 65534) new pix_fmt's.

Originally committed as revision 8704 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Ivo van Poorten 2007-04-10 09:15:54 +00:00
parent e457023a95
commit 201df5a19f
1 changed files with 24 additions and 2 deletions
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26
libavcodec/pnm.c
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@ -26,6 +26,7 @@ typedef struct PNMContext {
uint8_t *bytestream_start;
uint8_t *bytestream_end;
AVFrame picture;
int maxval; ///< maximum value of a pixel
} PNMContext;
static inline int pnm_space(int c)
@ -142,8 +143,12 @@ static int pnm_decode_header(AVCodecContext *avctx, PNMContext * const s){
return -1;
if (avctx->pix_fmt != PIX_FMT_MONOWHITE) {
pnm_get(s, buf1, sizeof(buf1));
if(atoi(buf1) == 65535 && avctx->pix_fmt == PIX_FMT_GRAY8)
s->maxval = atoi(buf1);
if(s->maxval >= 256 && avctx->pix_fmt == PIX_FMT_GRAY8) {
avctx->pix_fmt = PIX_FMT_GRAY16BE;
if (s->maxval != 65535)
avctx->pix_fmt = PIX_FMT_GRAY16;
}
}
/* more check if YUV420 */
if (avctx->pix_fmt == PIX_FMT_YUV420P) {
@ -165,7 +170,7 @@ static int pnm_decode_frame(AVCodecContext *avctx,
PNMContext * const s = avctx->priv_data;
AVFrame *picture = data;
AVFrame * const p= (AVFrame*)&s->picture;
int i, n, linesize, h;
int i, n, linesize, h, upgrade = 0;
unsigned char *ptr;
s->bytestream_start=
@ -194,9 +199,14 @@ static int pnm_decode_frame(AVCodecContext *avctx,
goto do_read;
case PIX_FMT_GRAY8:
n = avctx->width;
if (s->maxval < 255)
upgrade = 1;
goto do_read;
case PIX_FMT_GRAY16BE:
case PIX_FMT_GRAY16LE:
n = avctx->width * 2;
if (s->maxval < 65535)
upgrade = 2;
goto do_read;
case PIX_FMT_MONOWHITE:
case PIX_FMT_MONOBLACK:
@ -207,7 +217,19 @@ static int pnm_decode_frame(AVCodecContext *avctx,
if(s->bytestream + n*avctx->height > s->bytestream_end)
return -1;
for(i = 0; i < avctx->height; i++) {
if (!upgrade)
memcpy(ptr, s->bytestream, n);
else if (upgrade == 1) {
unsigned int j, f = (255*128 + s->maxval/2) / s->maxval;
for (j=0; j<n; j++)
ptr[j] = (s->bytestream[j] * f + 64) >> 7;
} else if (upgrade == 2) {
unsigned int j, v, f = (65535*32768 + s->maxval/2) / s->maxval;
for (j=0; j<n/2; j++) {
v = be2me_16(((uint16_t *)s->bytestream)[j]);
((uint16_t *)ptr)[j] = (v * f + 16384) >> 15;
}
}
s->bytestream += n;
ptr += linesize;
}