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decode: expose zlib FLEVEL for images (#204)

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Randy 2022-02-09 23:56:04 +01:00 committed by GitHub
parent 93b2e4e8f6
commit 4baa1b1384
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2 changed files with 54 additions and 1 deletions
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23
spng/spng.c
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@ -3623,10 +3623,31 @@ int spng_decode_image(spng_ctx *ctx, void *out, size_t len, int fmt, int flags)
if(len < ctx->image_size) return SPNG_EBUFSIZ;
}
uint32_t bytes_read = 0;
ret = read_idat_bytes(ctx, &bytes_read);
if(ret) return decode_err(ctx, ret);
if(bytes_read > 1)
{
int valid = read_u16(ctx->data) % 31 ? 0 : 1;
unsigned flg = ctx->data[1];
unsigned flevel = flg >> 6;
int compression_level = Z_DEFAULT_COMPRESSION;
if(flevel == 0) compression_level = 0; /* fastest */
else if(flevel == 1) compression_level = 1; /* fast */
else if(flevel == 2) compression_level = 6; /* default */
else if(flevel == 3) compression_level = 9; /* slowest, max compression */
if(valid) ctx->image_options.compression_level = compression_level;
}
ret = spng__inflate_init(ctx, ctx->image_options.window_bits);
if(ret) return decode_err(ctx, ret);
ctx->zstream.avail_in = 0;
ctx->zstream.avail_in = bytes_read;
ctx->zstream.next_in = ctx->data;
size_t scanline_buf_size = ctx->subimage[ctx->widest_pass].scanline_width;

32
tests/testsuite.c
View File

@ -1422,6 +1422,10 @@ static int extended_tests(FILE *file, int fmt)
struct spng_plte plte = {0};
static unsigned char chunk_data[9000];
/* NOTE: This value is compressed to 2 bits by zlib, it's not a 1:1 mapping */
int compression_level = 0;
int expected_compression_level = 0;
spng_set_png_file(dec, file);
spng_get_ihdr(dec, &ihdr);
@ -1435,6 +1439,7 @@ static int extended_tests(FILE *file, int fmt)
enc = spng_ctx_new(SPNG_CTX_ENCODER);
spng_set_option(enc, SPNG_ENCODE_TO_BUFFER, 1);
spng_set_option(enc, SPNG_IMG_COMPRESSION_LEVEL, compression_level);
spng_set_ihdr(enc, &ihdr);
@ -1475,6 +1480,31 @@ static int extended_tests(FILE *file, int fmt)
}
spng_ctx_free(enc);
enc = NULL;
/* Verify the image's zlib FLEVEL */
spng_ctx_free(dec);
dec = spng_ctx_new(0);
spng_set_png_buffer(dec, encoded, bytes_encoded);
spng_decode_image(dec, NULL, 0, SPNG_FMT_PNG, SPNG_DECODE_PROGRESSIVE);
ret = spng_get_option(dec, SPNG_IMG_COMPRESSION_LEVEL, &compression_level);
if(ret || (compression_level != expected_compression_level) )
{
if(ret) printf("error getting image compression level: %s\n", spng_strerror(ret));
else
{
printf("unexpected compression level (expected %d, got %d)\n",
expected_compression_level,
compression_level);
ret = 1;
}
goto cleanup;
}
/* Reencode the same image but to a stream this time */
enc = spng_ctx_new(SPNG_CTX_ENCODER);
@ -1483,6 +1513,8 @@ static int extended_tests(FILE *file, int fmt)
spng_set_png_stream(enc, stream_write_checked, &state);
spng_set_option(enc, SPNG_IMG_COMPRESSION_LEVEL, compression_level);
spng_set_ihdr(enc, &ihdr);
if(plte.n_entries) spng_set_plte(enc, &plte);