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Add palette index check support #238

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Add palette index check support #238

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1 change: 1 addition & 0 deletions docs/decode.md
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Original file line number Diff line number Diff line change
Expand Up @@ -322,6 +322,7 @@ If the image is not interlaced this function's behavior is identical to
| `SPNG_IMG_COMPRESSION_LEVEL` | `-1` | May expose an estimate (0-9) after `spng_decode_image()` |
| `SPNG_IMG_WINDOW_BITS` | `15`* | Set zlib window bits used for image decompression |
| `SPNG_CHUNK_COUNT_LIMIT` | `1000` | Limit shared by both known and unknown chunks |
| `SPNG_CHECK_PALETTE_INDEX` | `0` | Check image for invalid palette indices |

\* Option may be optimized if not set explicitly.

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25 changes: 13 additions & 12 deletions docs/encode.md
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Expand Up @@ -186,18 +186,19 @@ On success the buffer must be freed by the user.

# Encode options

| Option | Default value | Description |
|----------------------------------|---------------------------|-----------------------------------|
| `SPNG_IMG_COMPRESSION_LEVEL` | `Z_DEFAULT_COMPRESSION` | Set image compression level (0-9) |
| `SPNG_IMG_WINDOW_BITS` | `15`* | Set image zlib window bits (9-15) |
| `SPNG_IMG_MEM_LEVEL` | `8` | Set zlib `memLevel` for images |
| `SPNG_IMG_COMPRESSION_STRATEGY` | `Z_FILTERED`* | Set image compression strategy |
| `SPNG_TEXT_COMPRESSION_LEVEL` | `Z_DEFAULT_COMPRESSION` | Set text compression level (0-9) |
| `SPNG_TEXT_WINDOW_BITS` | `15` | Set text zlib window bits (9-15) |
| `SPNG_TEXT_MEM_LEVEL` | `8` | Set zlib `memLevel` for text |
| `SPNG_TEXT_COMPRESSION_STRATEGY` | `Z_DEFAULT_STRATEGY` | Set text compression strategy |
| `SPNG_FILTER_CHOICE` | `SPNG_FILTER_CHOICE_ALL`* | Configure or disable filtering |
| `SPNG_ENCODE_TO_BUFFER` | `0` | Encode to internal buffer |
| Option | Default value | Description |
|----------------------------------|---------------------------|-----------------------------------------|
| `SPNG_IMG_COMPRESSION_LEVEL` | `Z_DEFAULT_COMPRESSION` | Set image compression level (0-9) |
| `SPNG_IMG_WINDOW_BITS` | `15`* | Set image zlib window bits (9-15) |
| `SPNG_IMG_MEM_LEVEL` | `8` | Set zlib `memLevel` for images |
| `SPNG_IMG_COMPRESSION_STRATEGY` | `Z_FILTERED`* | Set image compression strategy |
| `SPNG_TEXT_COMPRESSION_LEVEL` | `Z_DEFAULT_COMPRESSION` | Set text compression level (0-9) |
| `SPNG_TEXT_WINDOW_BITS` | `15` | Set text zlib window bits (9-15) |
| `SPNG_TEXT_MEM_LEVEL` | `8` | Set zlib `memLevel` for text |
| `SPNG_TEXT_COMPRESSION_STRATEGY` | `Z_DEFAULT_STRATEGY` | Set text compression strategy |
| `SPNG_FILTER_CHOICE` | `SPNG_FILTER_CHOICE_ALL`* | Configure or disable filtering |
| `SPNG_ENCODE_TO_BUFFER` | `0` | Encode to internal buffer |
| `SPNG_CHECK_PALETTE_INDEX` | `1` | Check image for invalid palette indices |

\* Option may be optimized if not set explicitly.

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1 change: 1 addition & 0 deletions docs/migrate-libpng.md
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Expand Up @@ -389,3 +389,4 @@ Filter choice flags for [`spng_set_option()`](context.md#spng_set_option) when u
| `png_write_chunk_start()` | N/A | Not supported |
| `png_write_chunk_data()` | N/A | Not supported |
| `png_write_chunk_end()` | N/A | Not supported |
| `png_set_check_for_invalid_index()` | `spng_set_option()` | `SPNG_CHECK_PALETTE_INDEX` |
58 changes: 58 additions & 0 deletions spng/spng.c
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Expand Up @@ -263,6 +263,7 @@ struct spng_ctx

unsigned streaming: 1;
unsigned internal_buffer: 1; /* encoding to internal buffer */
unsigned check_indices: 1;

unsigned inflate: 1;
unsigned deflate: 1;
Expand Down Expand Up @@ -1782,6 +1783,33 @@ static inline void gamma_correct_row(unsigned char *row, uint32_t pixels, int fm
}
}

static int check_indices(unsigned char *scanline, uint32_t width, unsigned bit_depth, uint32_t n_entries)
{
int i;
unsigned int max = n_entries - 1;

if(bit_depth < 8)
{
struct spng__iter iter = spng__iter_init(bit_depth, scanline);

for(i=0; i < width; i++)
{
uint8_t sample = get_sample(&iter);

if(sample > max) return SPNG_EPLTE_IDX;
}
}
else
{
for(i=0; i < width; i++)
{
if(scanline[i] > max) return SPNG_EPLTE_IDX;
}
}

return 0;
}

/* Apply transparency to output row */
static inline void trns_row(unsigned char *row,
const unsigned char *scanline,
Expand Down Expand Up @@ -3332,6 +3360,13 @@ int spng_decode_scanline(spng_ctx *ctx, void *out, size_t len)

scanline = ctx->scanline;

if(ctx->ihdr.color_type == SPNG_COLOR_TYPE_INDEXED && ctx->check_indices)
{
ret = check_indices(scanline, scanline_width, ihdr->bit_depth, ctx->plte.n_entries);

if(ret) return decode_err(ctx, ret);
}

for(k=0; k < width; k++)
{
pixel = (unsigned char*)out + pixel_offset;
Expand Down Expand Up @@ -4575,6 +4610,13 @@ static int encode_scanline(spng_ctx *ctx, const void *scanline, size_t len)
/* encode_row() interlaces directly to ctx->scanline */
if(scanline != ctx->scanline) memcpy(ctx->scanline, scanline, scanline_width - 1);

if(ctx->ihdr.color_type == SPNG_COLOR_TYPE_INDEXED && ctx->check_indices)
{
ret = check_indices(ctx->scanline, scanline_width, ctx->ihdr.bit_depth, ctx->plte.n_entries);

if(ret) return encode_err(ctx, ret);
}

if(f.to_bigendian) u16_row_to_bigendian(ctx->scanline, scanline_width - 1);
const int requires_previous = f.filter_choice & (SPNG_FILTER_CHOICE_UP | SPNG_FILTER_CHOICE_AVG | SPNG_FILTER_CHOICE_PAETH);

Expand Down Expand Up @@ -5272,6 +5314,15 @@ int spng_set_option(spng_ctx *ctx, enum spng_option option, int value)

break;
}
case SPNG_CHECK_PALETTE_INDEX:
{
if(value < 0) return 1;

if(!value) ctx->check_indices = 0;
else ctx->check_indices = 1;

break;
}
default: return 1;
}

Expand Down Expand Up @@ -5350,6 +5401,13 @@ int spng_get_option(spng_ctx *ctx, enum spng_option option, int *value)

break;
}
case SPNG_CHECK_PALETTE_INDEX:
{
if(ctx->check_indices) *value = 1;
else *value = 0;

break;
}
default: return 1;
}

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1 change: 1 addition & 0 deletions spng/spng.h
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Expand Up @@ -409,6 +409,7 @@ enum spng_option
SPNG_FILTER_CHOICE,
SPNG_CHUNK_COUNT_LIMIT,
SPNG_ENCODE_TO_BUFFER,
SPNG_CHECK_PALETTE_INDEX,
};

typedef void* SPNG_CDECL spng_malloc_fn(size_t size);
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