Module: graphics.image.png

Source: ./graphics/image/png.reef

Overview

graphics/image/png.reef - PNG file format loader Part of reef-stdlib graphics module

This module provides PNG (Portable Network Graphics) file loading. Uses system zlib for DEFLATE decompression via FFI. Supports: Grayscale, RGB, Indexed (palette), GrayAlpha, RGBA Supports: 8-bit and 16-bit depth (16-bit downsampled to 8-bit)

Types

PngResult

Fields:

Name	Type
`ok`	`bool`
`img`	`image.Image`
`error_msg`	`string`

PngChunk

Fields:

Name	Type
`length`	`int`
`chunk_type`	`string`
`data_offset`	`int`
`crc`	`int`

IhdrData

IHDR data

Fields:

Name	Type
`width`	`int`
`height`	`int`
`bit_depth`	`int`
`color_type`	`int`
`compression`	`int`
`filter_method`	`int`
`interlace`	`int`

EncoderOutput

Holder for an encoder output buffer + its valid length.

Fields:

Name	Type
`buffer`	`[uint8]`
`length`	`int`

Functions

`fn png_result_ok(result: PngResult): bool`

`fn png_result_image(result: PngResult): image.Image`

`fn png_result_error(result: PngResult): string`

`fn make_png_error(msg: string): PngResult`

`fn make_png_ok(img: image.Image): PngResult`

`fn read_u8(data: [int], offset: int): int`

`fn read_u32_be(data: [int], offset: int): int`

`fn read_chunk_type(data: [int], offset: int): string`

`fn string_to_bytes(s: string): [int]`

`fn validate_png_signature(data: [int]): bool`

`fn parse_chunk(data: [int], offset: int): PngChunk`

`fn chunk_size(chunk: PngChunk): int`

`fn parse_ihdr(data: [int], chunk: PngChunk): IhdrData`

`fn bytes_per_pixel(color_type: int, bit_depth: int): int`

`fn paeth_predictor(a: int, b: int, c: int): int`

`fn total_idat_size(data: [int], start_offset: int): int`

Sum IDAT chunk lengths without copying; returns a value strictly greater than the cap if the total overflows or exceeds it, so the caller can reject before any allocation. Cap = 67108864.

`fn collect_idat_data(data: [int], start_offset: int): [int]`

`fn parse_palette(data: [int], start_offset: int): [core.Color]`

`fn decompress_idat(idat_data: [int], expected_size: int): [int]`

`fn decode_pixel(scanline: [int], x: int, color_type: int, palette: [core.Color]): core.Color`

`fn decode_scanlines(raw_data: [int], ihdr: IhdrData, palette: [core.Color]): image.Image`

`fn load_png(filepath: string): PngResult`

`fn load_png_bytes(data: [int]): PngResult`

`fn png_color_type_for_format(format: image.PixelFormat): int`

Determine PNG color type for an Image's pixel format

`fn png_bpp_for_color_type(color_type: int): int`

Bytes per pixel in the encoded raw PNG stream for a color type

`fn build_raw_image_data(img: image.Image, color_type: int, total_out: int): [uint8]`

Build the raw, unfiltered PNG image data into a calloc-backed [byte] suitable for passing to zlib_compress. Each scanline is prefixed with filter byte 0 (None), with pixels in PNG channel order.

`fn chunk_crc(chunk_type: string, data: [uint8], data_len: int): int`

Compute CRC32 over chunk type (4 ASCII bytes) plus chunk data. Uses the incremental crc32 API so we don't need to splice arrays.

`fn write_chunk(out: [uint8], offset: int, chunk_type: string, data: [uint8], data_len: int): int`

Write a PNG chunk (length + type + data + CRC) into out at offset. Returns the new offset after the chunk.

`fn encode_png_internal(img: image.Image): EncoderOutput`

Internal: produce the encoded PNG into a calloc-backed [byte] plus its length.

`fn encode_png_bytes(img: image.Image): [uint8]`

`fn save_png(filepath: string, img: image.Image): bool`

Procedures

`proc apply_filter(filter_type: int, scanline: [int], prev_scanline: [int], bpp: int, width: int)`

`proc write_u32_be(buf: [uint8], offset: int, value: int)`

Write a 32-bit big-endian integer into a [byte] buffer at offset. Treats the int as the low 32 bits (so negative ints are handled as their two's-complement byte pattern).

Generated by reefc doc