Hi!
Attached patch allows reading the pgm file that jasper creates
using the jpeg 2000 reference file p0_03.j2k as input.
Please comment, Carl Eugen
From 5da97c417d66b1e840b1feae31f0852cf3755c39 Mon Sep 17 00:00:00 2001
From: Carl Eugen Hoyos <ceffm...@gmail.com>
Date: Sat, 25 Apr 2020 17:05:40 +0200
Subject: [PATCH] lavc/pnm: Allow reading signed pgm values as written by
jasper.
---
libavcodec/pnm.c | 4 ++++
libavcodec/pnm.h | 1 +
libavcodec/pnmdec.c | 2 +-
3 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/libavcodec/pnm.c b/libavcodec/pnm.c
index b5c2881948..c9b9eb9ccd 100644
--- a/libavcodec/pnm.c
+++ b/libavcodec/pnm.c
@@ -176,6 +176,10 @@ int ff_pnm_decode_header(AVCodecContext *avctx, PNMContext * const s)
if (avctx->pix_fmt != AV_PIX_FMT_MONOWHITE && avctx->pix_fmt != AV_PIX_FMT_MONOBLACK) {
pnm_get(s, buf1, sizeof(buf1));
s->maxval = atoi(buf1);
+ if (s->maxval < 0) {
+ s->maxval *= -1;
+ s->jasper_signed = 1;
+ }
if (s->maxval <= 0 || s->maxval > UINT16_MAX) {
av_log(avctx, AV_LOG_ERROR, "Invalid maxval: %d\n", s->maxval);
s->maxval = 255;
diff --git a/libavcodec/pnm.h b/libavcodec/pnm.h
index 5bc0aad29f..2550cef92b 100644
--- a/libavcodec/pnm.h
+++ b/libavcodec/pnm.h
@@ -30,6 +30,7 @@ typedef struct PNMContext {
uint8_t *bytestream_end;
int maxval; ///< maximum value of a pixel
int type;
+ int jasper_signed;
} PNMContext;
int ff_pnm_decode_header(AVCodecContext *avctx, PNMContext * const s);
diff --git a/libavcodec/pnmdec.c b/libavcodec/pnmdec.c
index dbcaef3884..6e5f5b6c3b 100644
--- a/libavcodec/pnmdec.c
+++ b/libavcodec/pnmdec.c
@@ -168,7 +168,7 @@ static int pnm_decode_frame(AVCodecContext *avctx, void *data,
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;
+ ptr[j] = ((s->bytestream[j] - (s->maxval / 2 - 1) * s->jasper_signed) * 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++) {
--
2.24.1
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