Decode

Data types

int spng_read_fn(spng_ctx *ctx, void *user, void *data, size_t n)

Type definition for callback passed to spng_set_png_stream().

A read callback function should copy “n” bytes to *data and return 0 or SPNG_IO_EOF/SPNG_IO_ERROR on error.

spng_format

enum spng_format
{
    SPNG_FMT_RGBA8 = 1,
    SPNG_FMT_RGBA16 = 2
};

spng_decode_flags

enum spng_decode_flags
{
    SPNG_DECODE_USE_TRNS = 1,
    SPNG_DECODE_USE_GAMA = 2,
    SPNG_DECODE_USE_SBIT = 8 /* Rescale samples using sBIT values */
};

API

int spng_set_png_buffer(spng_ctx *ctx, void *buf, size_t size)

Set PNG buffer, this can only be called once per context.

int spng_set_png_stream(spng_ctx *ctx, spng_read_fn *read_fn, void *user)

Set PNG stream, this can only be called once per context.

Note

PNG’s are read up to the file end marker, this is identical behavior to libpng.

int spng_decoded_image_size(spng_ctx *ctx, int fmt, size_t *out)

Calculates decoded image buffer size for the given output format.

An input file must be set.

int spng_decode_image(spng_ctx *ctx, void *out, size_t out_size, int fmt, int flags)

Decodes the PNG file and writes the decoded image to *out.

*out must point to a buffer of length out_size.

out_size must be equal to or greater than the number calculated with spng_decoded_image_size() with the same output format.

Interlaced images are written deinterlaced to *out.

Note

Common errors in PNG files such as oversized IDAT streams are ignored.