libavodec/exr : add support for Y and YA file (ticket #5621)

a gray channel in exr, is named Y
we admit that the file need to be interpreted as gray
only if no other channel match (except alpha)

to manage RGB and Y in the color conversion part of decode_block,
the color processing is now made with a for loop.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 61 insertions, 42 deletions

diff --git a/libavcodec/exr.c b/libavcodec/exr.c
index cabe329c7f..3c05873a01 100644
--- a/libavcodec/exr.c
+++ b/libavcodec/exr.c
@@ -129,6 +129,8 @@ typedef struct EXRContext {
     EXRTileAttribute tile_attr; /* header data attribute of tile */
     int is_tile; /* 0 if scanline, 1 if tile */
 
+    int is_luma;/* 1 if there is an Y plane */
+
     GetByteContext gb;
     const uint8_t *buf;
     int buf_size;
@@ -1033,6 +1035,7 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
     int axmax = (avctx->width - (s->xmax + 1)) * 2 * s->desc->nb_components; /* nb pixel to add at the right of the datawindow */
     int bxmin = s->xmin * 2 * s->desc->nb_components; /* nb pixel to add at the left of the datawindow */
     int i, x, buf_size = s->buf_size;
+    int c, rgb_channel_count;
     float one_gamma = 1.0f / s->gamma;
     avpriv_trc_function trc_func = avpriv_get_trc_function_from_trc(s->apply_trc_type);
     int ret;
@@ -1142,9 +1145,15 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
         src = td->uncompressed_data;
     }
 
+    if (!s->is_luma) {
     channel_buffer[0] = src + td->xsize * s->channel_offsets[0];
     channel_buffer[1] = src + td->xsize * s->channel_offsets[1];
     channel_buffer[2] = src + td->xsize * s->channel_offsets[2];
+    rgb_channel_count = 3;
+    } else { /* put y data in the first channel_buffer */
+        channel_buffer[0] = src + td->xsize * s->channel_offsets[1];
+        rgb_channel_count = 1;
+    }
     if (s->channel_offsets[3] >= 0)
         channel_buffer[3] = src + td->xsize * s->channel_offsets[3];
 
@@ -1153,11 +1162,13 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
     for (i = 0;
          i < td->ysize; i++, ptr += p->linesize[0]) {
 
-        const uint8_t *r, *g, *b, *a;
+        const uint8_t * a;
+        const uint8_t *rgb[3];
+
+        for (c = 0; c < rgb_channel_count; c++){
+            rgb[c] = channel_buffer[c];
+        }
 
-        r = channel_buffer[0];
-        g = channel_buffer[1];
-        b = channel_buffer[2];
         if (channel_buffer[3])
             a = channel_buffer[3];
 
@@ -1172,37 +1183,26 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
             if (trc_func) {
                 for (x = 0; x < td->xsize; x++) {
                     union av_intfloat32 t;
-                    t.i = bytestream_get_le32(&r);
-                    t.f = trc_func(t.f);
-                    *ptr_x++ = exr_flt2uint(t.i);
-
-                    t.i = bytestream_get_le32(&g);
-                    t.f = trc_func(t.f);
-                    *ptr_x++ = exr_flt2uint(t.i);
 
-                    t.i = bytestream_get_le32(&b);
-                    t.f = trc_func(t.f);
-                    *ptr_x++ = exr_flt2uint(t.i);
+                    for (c = 0; c < rgb_channel_count; c++) {
+                        t.i = bytestream_get_le32(&rgb[c]);
+                        t.f = trc_func(t.f);
+                        *ptr_x++ = exr_flt2uint(t.i);
+                    }
                     if (channel_buffer[3])
                         *ptr_x++ = exr_flt2uint(bytestream_get_le32(&a));
                 }
             } else {
                 for (x = 0; x < td->xsize; x++) {
                     union av_intfloat32 t;
-                    t.i = bytestream_get_le32(&r);
-                    if (t.f > 0.0f)  /* avoid negative values */
-                        t.f = powf(t.f, one_gamma);
-                    *ptr_x++ = exr_flt2uint(t.i);
-
-                    t.i = bytestream_get_le32(&g);
-                    if (t.f > 0.0f)
-                        t.f = powf(t.f, one_gamma);
-                    *ptr_x++ = exr_flt2uint(t.i);
-
-                    t.i = bytestream_get_le32(&b);
-                    if (t.f > 0.0f)
-                        t.f = powf(t.f, one_gamma);
-                    *ptr_x++ = exr_flt2uint(t.i);
+
+                    for (int c = 0; c < rgb_channel_count; c++) {
+                        t.i = bytestream_get_le32(&rgb[c]);
+                        if (t.f > 0.0f)  /* avoid negative values */
+                            t.f = powf(t.f, one_gamma);
+                        *ptr_x++ = exr_flt2uint(t.i);
+                    }
+
                     if (channel_buffer[3])
                         *ptr_x++ = exr_flt2uint(bytestream_get_le32(&a));
                 }
@@ -1210,9 +1210,10 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
         } else {
             // 16-bit
             for (x = 0; x < td->xsize; x++) {
-                *ptr_x++ = s->gamma_table[bytestream_get_le16(&r)];
-                *ptr_x++ = s->gamma_table[bytestream_get_le16(&g)];
-                *ptr_x++ = s->gamma_table[bytestream_get_le16(&b)];
+                for (int c = 0; c < rgb_channel_count; c++) {
+                    *ptr_x++ = s->gamma_table[bytestream_get_le16(&rgb[c])];
+                }
+
                 if (channel_buffer[3])
                     *ptr_x++ = exr_halflt2uint(bytestream_get_le16(&a));
             }
@@ -1296,6 +1297,7 @@ static int decode_header(EXRContext *s)
     s->tile_attr.xSize    = -1;
     s->tile_attr.ySize    = -1;
     s->is_tile            = 0;
+    s->is_luma            = 0;
 
     if (bytestream2_get_bytes_left(&s->gb) < 10) {
         av_log(s->avctx, AV_LOG_ERROR, "Header too short to parse.\n");
@@ -1363,17 +1365,22 @@ static int decode_header(EXRContext *s)
                 if (layer_match) { /* only search channel if the layer match is valid */
                     if (!strcmp(ch_gb.buffer, "R") ||
                         !strcmp(ch_gb.buffer, "X") ||
-                        !strcmp(ch_gb.buffer, "U"))
+                        !strcmp(ch_gb.buffer, "U")) {
                         channel_index = 0;
-                    else if (!strcmp(ch_gb.buffer, "G") ||
-                             !strcmp(ch_gb.buffer, "Y") ||
-                             !strcmp(ch_gb.buffer, "V"))
+                        s->is_luma = 0;
+                    } else if (!strcmp(ch_gb.buffer, "G") ||
+                               !strcmp(ch_gb.buffer, "V")) {
                         channel_index = 1;
-                    else if (!strcmp(ch_gb.buffer, "B") ||
-                             !strcmp(ch_gb.buffer, "Z") ||
-                             !strcmp(ch_gb.buffer, "W"))
-                        channel_index = 2;
-                    else if (!strcmp(ch_gb.buffer, "A"))
+                        s->is_luma = 0;
+                    } else if (!strcmp(ch_gb.buffer, "Y")) {
+                        channel_index = 1;
+                        s->is_luma = 1;
+                    } else if (!strcmp(ch_gb.buffer, "B") ||
+                               !strcmp(ch_gb.buffer, "Z") ||
+                               !strcmp(ch_gb.buffer, "W")){
+                               channel_index = 2;
+                        s->is_luma = 0;
+                    } else if (!strcmp(ch_gb.buffer, "A"))
                         channel_index = 3;
                     else
                         av_log(s->avctx, AV_LOG_WARNING,
@@ -1400,6 +1407,7 @@ static int decode_header(EXRContext *s)
                 bytestream2_skip(&ch_gb, 4);
                 xsub = bytestream2_get_le32(&ch_gb);
                 ysub = bytestream2_get_le32(&ch_gb);
+
                 if (xsub != 1 || ysub != 1) {
                     avpriv_report_missing_feature(s->avctx,
                                                   "Subsampling %dx%d",
@@ -1434,6 +1442,7 @@ static int decode_header(EXRContext *s)
 
             /* Check if all channels are set with an offset or if the channels
              * are causing an overflow  */
+            if (!s->is_luma){/* if we expected to have at least 3 channels */
             if (FFMIN3(s->channel_offsets[0],
                        s->channel_offsets[1],
                        s->channel_offsets[2]) < 0) {
@@ -1445,6 +1454,7 @@ static int decode_header(EXRContext *s)
                     av_log(s->avctx, AV_LOG_ERROR, "Missing blue channel.\n");
                 return AVERROR_INVALIDDATA;
             }
+            }
 
             // skip one last byte and update main gb
             s->gb.buffer = ch_gb.buffer + 1;
@@ -1594,10 +1604,19 @@ static int decode_frame(AVCodecContext *avctx, void *data,
     switch (s->pixel_type) {
     case EXR_FLOAT:
     case EXR_HALF:
-        if (s->channel_offsets[3] >= 0)
+        if (s->channel_offsets[3] >= 0) {
+            if (!s->is_luma) {
             avctx->pix_fmt = AV_PIX_FMT_RGBA64;
-        else
+            } else {
+                avctx->pix_fmt = AV_PIX_FMT_YA16;
+            }
+        } else {
+            if (!s->is_luma) {
             avctx->pix_fmt = AV_PIX_FMT_RGB48;
+            } else {
+                avctx->pix_fmt = AV_PIX_FMT_GRAY16;
+            }
+        }
         break;
     case EXR_UINT:
         avpriv_request_sample(avctx, "32-bit unsigned int");