Breaking API changes for 1.0.0 about libspng

[randy408]

3d94f11 deprecates SPNG_DECODE_USE_* flags.

[randy408]

struct spng_bkgd.plte_index is an uint16_t, it should be uint8_t.

[randy408]

Consider combining spng_ctx_new() and spng_ctx_new2() and changing the return value to int.

[randy408]

Consider renaming spng_set_png_buffer/stream() to something like spng_set_src_buffer/stream() to allow for more consistent function names once encode support is added, functions for setting the output buffer/stream for the encoder would be named spng_set_dst_buffer/stream().

[randy408]

New types could be introduced as typedefs to spng_ctx:

• spng_dec - decoder
• spng_enc - encoder

To simplify the API and make things clearer:

• spng_set_*() functions would be changed to take spng_enc*
• Functions for context creation and setting of source/destination PNG can be merged:
• int spng_new_buffer_decoder(spng_dec**, spng_alloc*, int flags, void *buf, size_t len);
• int spng_new_stream_decoder(spng_dec**, spng_alloc*, int flags, spng_read_fn*, void *user);
• int spng_new_stream_encoder(spng_enc**, spng_alloc*, int flags, spng_write_fn*, void *user);

These functions could also be added without introducing the typedefs, spng_new_buffer_decoder() is more descriptive than spng_ctx_new() + spng_set_src_buffer().

[randy408]

spng_get_text() and spng_get_splt() should use regular int pointers for array counts and check for INT32_MAX instead of checking for unsigned overflow when adding a new entry to its internal list, the list should also be assigned to a pointer instead of making the user allocate a struct array:

spng_get_text(spng_ctx*, struct spng_text **text, int *n_text);

struct spng_text should also change to reflect the internal version.

[randy408]

Progressive encode/decode functions should probably not return SPNG_EOI on the last row (#205).

[randy408]

struct spng_chunk should have been removed from the header before the API was stabilized, this led to struct spng_unknown_chunk as a workaround.

Consider renaming the latter to the former and shortening spng_set/get_unknown_chunks() too.

[randy408]

struct spng_ihdr.color_type is currently uint8_t, enum spng_color_type would be better.

[randy408]

Consider widening struct spng_offs.unit_specifier and struct spng_phys.unit_specifier to enums.

edit: struct spng_row_info.filter and struct spng_ihdr.interlace_method too