| // Copyright 2024 The Wuffs Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| // |
| // SPDX-License-Identifier: Apache-2.0 OR MIT |
| |
| // -------- |
| |
| // Thumbhash is a tiny image format (maximum image dimensions are 32×32 pixels; |
| // maximum image file size is 29 bytes or 32 bytes with a 3-byte header), based |
| // on the Discrete Cosine Transform. |
| // |
| // https://evanw.github.io/thumbhash/ has the original description and |
| // implementation. This implementation assumes a 3-byte magic identifier is |
| // prepended, unless QUIRK_JUST_RAW_THUMBHASH is enabled, so that /usr/bin/file |
| // or similar programs can identify the data as thumbhash-formatted data. |
| // |
| // That 3-byte magic string is "\xC3\xBE\xFE", which is arbitrary and not part |
| // of the original thumbhash description or implementation. But "\xC3\xBE" is |
| // the UTF-8 encoding of 'þ' (U+00FE LATIN SMALL LETTER THORN) and "\xFE" is |
| // invalid UTF-8 but is the ISO-8859-1 encoding of 'þ'. The Old English letter |
| // 'þ' is pronounced like the "th" that starts "thumbhash". |
| // |
| // This implementation also uses fixed point math instead of floating point. |
| |
| pub status "#bad header" |
| pub status "#truncated input" |
| |
| pub const DECODER_WORKBUF_LEN_MAX_INCL_WORST_CASE : base.u64 = 0 |
| |
| pub struct decoder? implements base.image_decoder( |
| pixfmt : base.u32, |
| width : base.u32[..= 32], |
| height : base.u32[..= 32], |
| |
| // The call sequence state machine is discussed in |
| // (/doc/std/image-decoders-call-sequence.md). |
| call_sequence : base.u8, |
| |
| swizzler : base.pixel_swizzler, |
| util : base.utility, |
| ) + ( |
| pixels : array[32] array[128] base.u8, |
| ) |
| |
| pub func decoder.get_quirk(key: base.u32) base.u64 { |
| return 0 |
| } |
| |
| pub func decoder.set_quirk!(key: base.u32, value: base.u64) base.status { |
| return base."#unsupported option" |
| } |
| |
| pub func decoder.decode_image_config?(dst: nptr base.image_config, src: base.io_reader) { |
| var status : base.status |
| |
| while true { |
| status =? this.do_decode_image_config?(dst: args.dst, src: args.src) |
| if (status == base."$short read") and args.src.is_closed() { |
| return "#truncated input" |
| } |
| yield? status |
| } |
| } |
| |
| pri func decoder.do_decode_image_config?(dst: nptr base.image_config, src: base.io_reader) { |
| var c32 : base.u32 |
| |
| if this.call_sequence <> 0x00 { |
| return base."#bad call sequence" |
| } |
| |
| // TODO: implement QUIRK_JUST_RAW_THUMBHASH. |
| c32 = args.src.read_u24le_as_u32?() |
| if c32 <> '\xC3\xBE\xFE'le { |
| return "#bad header" |
| } |
| |
| this.pixfmt = base.PIXEL_FORMAT__BGRX |
| this.width = 32 |
| this.height = 32 |
| |
| if args.dst <> nullptr { |
| args.dst.set!( |
| pixfmt: this.pixfmt, |
| pixsub: 0, |
| width: this.width, |
| height: this.height, |
| first_frame_io_position: 3, |
| first_frame_is_opaque: this.pixfmt == base.PIXEL_FORMAT__BGRX) |
| } |
| |
| this.call_sequence = 0x20 |
| } |
| |
| pub func decoder.decode_frame_config?(dst: nptr base.frame_config, src: base.io_reader) { |
| var status : base.status |
| |
| while true { |
| status =? this.do_decode_frame_config?(dst: args.dst, src: args.src) |
| if (status == base."$short read") and args.src.is_closed() { |
| return "#truncated input" |
| } |
| yield? status |
| } |
| } |
| |
| pri func decoder.do_decode_frame_config?(dst: nptr base.frame_config, src: base.io_reader) { |
| if this.call_sequence == 0x20 { |
| // No-op. |
| } else if this.call_sequence < 0x20 { |
| this.do_decode_image_config?(dst: nullptr, src: args.src) |
| } else if this.call_sequence == 0x28 { |
| if 3 <> args.src.position() { |
| return base."#bad restart" |
| } |
| } else if this.call_sequence == 0x40 { |
| this.call_sequence = 0x60 |
| return base."@end of data" |
| } else { |
| return base."@end of data" |
| } |
| |
| if args.dst <> nullptr { |
| args.dst.set!(bounds: this.util.make_rect_ie_u32( |
| min_incl_x: 0, |
| min_incl_y: 0, |
| max_excl_x: this.width, |
| max_excl_y: this.height), |
| duration: 0, |
| index: 0, |
| io_position: 3, |
| disposal: 0, |
| opaque_within_bounds: this.pixfmt == base.PIXEL_FORMAT__BGRX, |
| overwrite_instead_of_blend: false, |
| background_color: 0x0000_0000) |
| } |
| |
| this.call_sequence = 0x40 |
| } |
| |
| pub func decoder.decode_frame?(dst: ptr base.pixel_buffer, src: base.io_reader, blend: base.pixel_blend, workbuf: slice base.u8, opts: nptr base.decode_frame_options) { |
| var status : base.status |
| |
| while true { |
| status =? this.do_decode_frame?(dst: args.dst, src: args.src, blend: args.blend, workbuf: args.workbuf, opts: args.opts) |
| if (status == base."$short read") and args.src.is_closed() { |
| return "#truncated input" |
| } |
| yield? status |
| } |
| } |
| |
| pri func decoder.do_decode_frame?(dst: ptr base.pixel_buffer, src: base.io_reader, blend: base.pixel_blend, workbuf: slice base.u8, opts: nptr base.decode_frame_options) { |
| var status : base.status |
| |
| if this.call_sequence == 0x40 { |
| // No-op. |
| } else if this.call_sequence < 0x40 { |
| this.do_decode_frame_config?(dst: nullptr, src: args.src) |
| } else { |
| return base."@end of data" |
| } |
| |
| status = this.swizzler.prepare!( |
| dst_pixfmt: args.dst.pixel_format(), |
| dst_palette: args.dst.palette(), |
| src_pixfmt: this.util.make_pixel_format(repr: this.pixfmt), |
| src_palette: this.util.empty_slice_u8(), |
| blend: args.blend) |
| if not status.is_ok() { |
| return status |
| } |
| |
| this.from_src_to_pixels?(src: args.src) |
| status = this.from_pixels_to_dst!(dst: args.dst) |
| if not status.is_ok() { |
| return status |
| } |
| |
| this.call_sequence = 0x60 |
| } |
| |
| pri func decoder.from_src_to_pixels?(src: base.io_reader) { |
| var y : base.u32 |
| var x : base.u32 |
| |
| // TODO: actually implement the format. For now, fill in a placeholder |
| // blue-green gradient. |
| |
| y = 0 |
| while y < 32 { |
| x = 0 |
| while x < 32, |
| inv y < 32, |
| { |
| this.pixels[y][(4 * x) + 0] = (x * 8) as base.u8 |
| this.pixels[y][(4 * x) + 1] = (y * 8) as base.u8 |
| this.pixels[y][(4 * x) + 2] = 0x00 |
| this.pixels[y][(4 * x) + 3] = 0xFF |
| x += 1 |
| } |
| y += 1 |
| } |
| } |
| |
| pri func decoder.from_pixels_to_dst!(dst: ptr base.pixel_buffer) base.status { |
| var dst_pixfmt : base.pixel_format |
| var dst_bits_per_pixel : base.u32[..= 256] |
| var dst_bytes_per_pixel : base.u32[..= 32] |
| var dst_bytes_per_row : base.u64 |
| var tab : table base.u8 |
| var y : base.u32 |
| var dst : slice base.u8 |
| var src : slice base.u8 |
| |
| // TODO: the dst_pixfmt variable shouldn't be necessary. We should be able |
| // to chain the two calls: "args.dst.pixel_format().bits_per_pixel()". |
| dst_pixfmt = args.dst.pixel_format() |
| dst_bits_per_pixel = dst_pixfmt.bits_per_pixel() |
| if (dst_bits_per_pixel & 7) <> 0 { |
| return base."#unsupported option" |
| } |
| dst_bytes_per_pixel = dst_bits_per_pixel / 8 |
| dst_bytes_per_row = (this.width * dst_bytes_per_pixel) as base.u64 |
| tab = args.dst.plane(p: 0) |
| |
| while y < this.height { |
| assert y < 32 via "a < b: a < c; c <= b"(c: this.height) |
| src = this.pixels[y][.. this.width * 4] |
| |
| dst = tab.row_u32(y: y) |
| if dst_bytes_per_row < dst.length() { |
| dst = dst[.. dst_bytes_per_row] |
| } |
| |
| this.swizzler.swizzle_interleaved_from_slice!( |
| dst: dst, |
| dst_palette: args.dst.palette(), |
| src: src) |
| |
| y += 1 |
| } |
| |
| return ok |
| } |
| |
| pub func decoder.frame_dirty_rect() base.rect_ie_u32 { |
| return this.util.make_rect_ie_u32( |
| min_incl_x: 0, |
| min_incl_y: 0, |
| max_excl_x: this.width, |
| max_excl_y: this.height) |
| } |
| |
| pub func decoder.num_animation_loops() base.u32 { |
| return 0 |
| } |
| |
| pub func decoder.num_decoded_frame_configs() base.u64 { |
| if this.call_sequence > 0x20 { |
| return 1 |
| } |
| return 0 |
| } |
| |
| pub func decoder.num_decoded_frames() base.u64 { |
| if this.call_sequence > 0x40 { |
| return 1 |
| } |
| return 0 |
| } |
| |
| pub func decoder.restart_frame!(index: base.u64, io_position: base.u64) base.status { |
| if this.call_sequence < 0x20 { |
| return base."#bad call sequence" |
| } |
| if (args.index <> 0) or (args.io_position <> 3) { |
| return base."#bad argument" |
| } |
| this.call_sequence = 0x28 |
| return ok |
| } |
| |
| pub func decoder.set_report_metadata!(fourcc: base.u32, report: base.bool) { |
| // No-op. Thumbhash doesn't support metadata. |
| } |
| |
| pub func decoder.tell_me_more?(dst: base.io_writer, minfo: nptr base.more_information, src: base.io_reader) { |
| return base."#no more information" |
| } |
| |
| pub func decoder.workbuf_len() base.range_ii_u64 { |
| return this.util.make_range_ii_u64(min_incl: 0, max_incl: 0) |
| } |
