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avcodec/exr: Simple check for available channels

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The existing is_luma check is fragile as depending on the order
of channels it can be set or reset

No testcase

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer
2025-09-19 00:20:36 +02:00
parent dd092f7fd9
commit 6e8cf0377f
1 changed files with 25 additions and 4 deletions
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libavcodec/exr.c
+25 -4
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@@ -175,6 +175,9 @@ typedef struct EXRContext {
int is_luma;/* 1 if there is an Y plane */
#define M(chr) (1<<chr - 'A')
int has_channel; ///< combinatin of flags representing the channel codes A-Z
GetByteContext gb;
const uint8_t *buf;
int buf_size;
@@ -1622,6 +1625,7 @@ static int decode_header(EXRContext *s, AVFrame *frame)
s->is_tile = 0;
s->is_multipart = 0;
s->is_luma = 0;
s->has_channel = 0;
s->current_part = 0;
if (bytestream2_get_bytes_left(gb) < 10) {
@@ -1725,23 +1729,26 @@ static int decode_header(EXRContext *s, AVFrame *frame)
}
if (layer_match) { /* only search channel if the layer match is valid */
if (strlen(ch_gb.buffer) == 1) {
int ch_chr = av_toupper(*ch_gb.buffer);
if (ch_chr >= 'A' && ch_chr <= 'Z')
s->has_channel |= M(ch_chr);
av_log(s->avctx, AV_LOG_DEBUG, "%c\n", ch_chr);
}
if (!av_strcasecmp(ch_gb.buffer, "R") ||
!av_strcasecmp(ch_gb.buffer, "X") ||
!av_strcasecmp(ch_gb.buffer, "U")) {
channel_index = 0;
s->is_luma = 0;
} else if (!av_strcasecmp(ch_gb.buffer, "G") ||
!av_strcasecmp(ch_gb.buffer, "V")) {
channel_index = 1;
s->is_luma = 0;
} else if (!av_strcasecmp(ch_gb.buffer, "Y")) {
channel_index = 1;
s->is_luma = 1;
} else if (!av_strcasecmp(ch_gb.buffer, "B") ||
!av_strcasecmp(ch_gb.buffer, "Z") ||
!av_strcasecmp(ch_gb.buffer, "W")) {
channel_index = 2;
s->is_luma = 0;
} else if (!av_strcasecmp(ch_gb.buffer, "A")) {
channel_index = 3;
} else {
@@ -1817,6 +1824,20 @@ static int decode_header(EXRContext *s, AVFrame *frame)
s->current_channel_offset += 4;
}
}
if (!((M('R') + M('G') + M('B')) & ~s->has_channel)) {
s->is_luma = 0;
} else if (!((M('X') + M('Y') + M('Z')) & ~s->has_channel)) {
s->is_luma = 0;
} else if (!((M('Y') + M('U') + M('V')) & ~s->has_channel)) {
s->is_luma = 0;
} else if (!((M('Y') ) & ~s->has_channel) &&
!((M('R') + M('G') + M('B') + M('U') + M('V') + M('X') + M('Z')) & s->has_channel)) {
s->is_luma = 1;
} else {
avpriv_request_sample(s->avctx, "Uncommon channel combination");
ret = AVERROR(AVERROR_PATCHWELCOME);
goto fail;
}
/* Check if all channels are set with an offset or if the channels
* are causing an overflow */