| // Copyright 2020 The Wuffs Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| use "std/crc32" |
| use "std/zlib" |
| |
| pub status "#bad checksum" |
| pub status "#bad chunk" |
| pub status "#bad filter" |
| pub status "#bad header" |
| pub status "#missing palette" |
| pub status "#unsupported PNG file" |
| |
| pri status "#internal error: inconsistent workbuf length" |
| pri status "#internal error: zlib decoder did not exhaust its input" |
| |
| pub const DECODER_WORKBUF_LEN_MAX_INCL_WORST_CASE : base.u64 = 0 |
| |
| pub struct decoder? implements base.image_decoder( |
| // The 0x00FF_FFFF limit is arbitrary (the PNG spec says 0x7FFF_FFFF) but |
| // it means that (width * height * bytes_per_pixel) doesn't overflow. |
| width : base.u32[..= 0x00FF_FFFF], |
| height : base.u32[..= 0x00FF_FFFF], |
| |
| // pass_bytes_per_row doesn't include the 1 byte for the per-row filter. |
| pass_bytes_per_row : base.u64[..= 0x07FF_FFF8], |
| |
| workbuf_wi : base.u64, |
| overall_workbuf_length : base.u64[..= 0x0007_FFFF_F100_0007], |
| pass_workbuf_length : base.u64[..= 0x0007_FFFF_F100_0007], |
| |
| // Call sequence states: |
| // - 0x00: initial state. |
| // - 0x03: image config decoded. |
| // - 0x04: frame config decoded. |
| // - 0xFF: end-of-data, usually after (the non-animated) frame decoded. |
| // |
| // State transitions: |
| // |
| // - 0x00 -> 0x03: via DIC |
| // - 0x00 -> 0x04: via DFC with implicit DIC |
| // - 0x00 -> 0xFF: via DF with implicit DIC and DFC |
| // |
| // - 0x03 -> 0x04: via DFC |
| // - 0x03 -> 0xFF: via DF with implicit DFC |
| // |
| // - 0x04 -> 0xFF: via DFC |
| // - 0x04 -> 0xFF: via DF |
| // |
| // - ???? -> 0x03: via RF for ???? > 0x00 |
| // |
| // Where: |
| // - DF is decode_frame |
| // - DFC is decode_frame_config, implicit means nullptr args.dst |
| // - DIC is decode_image_config, implicit means nullptr args.dst |
| // - RF is restart_frame |
| call_sequence : base.u8, |
| |
| ignore_checksum : base.bool, |
| |
| depth : base.u8[..= 16], |
| color_type : base.u8[..= 6], |
| filter_distance : base.u8[..= 8], |
| interlace_pass : base.u8[..= 7], |
| |
| seen_plte : base.bool, |
| seen_trns : base.bool, |
| |
| dst_pixfmt : base.u32, |
| src_pixfmt : base.u32, |
| |
| chunk_type : base.u32, |
| chunk_type_array : array[4] base.u8, |
| chunk_length : base.u64, |
| |
| frame_config_io_position : base.u64, |
| |
| swizzler : base.pixel_swizzler, |
| util : base.utility, |
| )( |
| crc32 : crc32.ieee_hasher, |
| zlib : zlib.decoder, |
| |
| dst_palette : array[4 * 256] base.u8, |
| src_palette : array[4 * 256] base.u8, |
| ) |
| |
| pub func decoder.set_quirk_enabled!(quirk: base.u32, enabled: base.bool) { |
| if args.quirk == base.QUIRK_IGNORE_CHECKSUM { |
| this.ignore_checksum = args.enabled |
| this.zlib.set_quirk_enabled!(quirk: args.quirk, enabled: args.enabled) |
| } |
| } |
| |
| pub func decoder.decode_image_config?(dst: nptr base.image_config, src: base.io_reader) { |
| var magic : base.u64 |
| var mark : base.u64 |
| var checksum_have : base.u32 |
| var checksum_want : base.u32 |
| var status : base.status |
| |
| if this.call_sequence <> 0 { |
| return base."#bad call sequence" |
| } |
| |
| magic = args.src.read_u64le?() |
| if magic <> '\x89PNG\x0D\x0A\x1A\x0A'le { |
| return "#bad header" |
| } |
| magic = args.src.read_u64le?() |
| if magic <> '\x00\x00\x00\x0DIHDR'le { |
| return "#bad header" |
| } |
| this.crc32.reset!() |
| this.chunk_type_array[0] = 'I' |
| this.chunk_type_array[1] = 'H' |
| this.chunk_type_array[2] = 'D' |
| this.chunk_type_array[3] = 'R' |
| this.crc32.update_u32!(x: this.chunk_type_array[..]) |
| |
| while true { |
| mark = args.src.mark() |
| status =? this.decode_ihdr?(src: args.src) |
| if not this.ignore_checksum { |
| checksum_have = this.crc32.update_u32!(x: args.src.since(mark: mark)) |
| } |
| if status.is_ok() { |
| break |
| } |
| yield? status |
| } endwhile |
| |
| // Verify CRC-32 checksum. |
| checksum_want = args.src.read_u32be?() |
| if (not this.ignore_checksum) and (checksum_have <> checksum_want) { |
| return "#bad checksum" |
| } |
| |
| // Read up until an IDAT chunk. |
| // |
| // By default, libpng "warns and discards" when seeing ancillary chunk |
| // checksum failures (as opposed to critical chunk checksum failures) but |
| // it still continues to decode the image. Wuffs' decoder is similar, |
| // simply always ignoring ancillary chunks' CRC-32 checksums. |
| // |
| // https://github.com/glennrp/libpng/blob/dbe3e0c43e549a1602286144d94b0666549b18e6/png.h#L1436 |
| // |
| // We've already seen the IHDR chunk. We're not expecting an IEND chunk. An |
| // IDAT chunk breaks the loop. The only other possible critical chunk is a |
| // PLTE chunk. We verify PLTE checksums here but ignore other checksums. |
| while true { |
| this.chunk_length = args.src.read_u32be_as_u64?() |
| this.chunk_type = args.src.read_u32le?() |
| if (not this.ignore_checksum) and |
| ((this.chunk_type == 'IDAT'le) or (this.chunk_type == 'PLTE'le)) { |
| this.crc32.reset!() |
| this.chunk_type_array[0] = ((this.chunk_type >> 0) & 0xFF) as base.u8 |
| this.chunk_type_array[1] = ((this.chunk_type >> 8) & 0xFF) as base.u8 |
| this.chunk_type_array[2] = ((this.chunk_type >> 16) & 0xFF) as base.u8 |
| this.chunk_type_array[3] = ((this.chunk_type >> 24) & 0xFF) as base.u8 |
| this.crc32.update_u32!(x: this.chunk_type_array[..]) |
| } |
| |
| if this.chunk_type == 'IDAT'le { |
| break |
| } |
| |
| while true { |
| mark = args.src.mark() |
| status =? this.decode_other_chunk?(src: args.src) |
| if (not this.ignore_checksum) and (this.chunk_type == 'PLTE'le) { |
| checksum_have = this.crc32.update_u32!(x: args.src.since(mark: mark)) |
| } |
| if status.is_ok() { |
| break |
| } |
| yield? status |
| } endwhile |
| checksum_want = args.src.read_u32be?() |
| if (not this.ignore_checksum) and (this.chunk_type == 'PLTE'le) and |
| (checksum_have <> checksum_want) { |
| return "#bad checksum" |
| } |
| |
| } endwhile |
| |
| if (this.color_type == 3) and (not this.seen_plte) { |
| return "#missing palette" |
| } |
| |
| this.frame_config_io_position = args.src.position() |
| |
| if args.dst <> nullptr { |
| args.dst.set!( |
| pixfmt: this.dst_pixfmt, |
| pixsub: 0, |
| width: this.width, |
| height: this.height, |
| first_frame_io_position: this.frame_config_io_position, |
| first_frame_is_opaque: (this.color_type <= 3) and (not this.seen_trns)) |
| } |
| |
| this.call_sequence = 3 |
| } |
| |
| pri func decoder.decode_ihdr?(src: base.io_reader) { |
| var a32 : base.u32 |
| var a8 : base.u8 |
| |
| a32 = args.src.read_u32be?() |
| if (a32 == 0) or (a32 >= 0x8000_0000) { |
| return "#bad header" |
| } else if a32 >= 0x0100_0000 { |
| return "#unsupported PNG file" |
| } |
| this.width = a32 |
| |
| a32 = args.src.read_u32be?() |
| if (a32 == 0) or (a32 >= 0x8000_0000) { |
| return "#bad header" |
| } else if a32 >= 0x0100_0000 { |
| return "#unsupported PNG file" |
| } |
| this.height = a32 |
| |
| // Depth. |
| a8 = args.src.read_u8?() |
| if a8 > 16 { |
| return "#bad header" |
| } |
| this.depth = a8 |
| |
| // Color. |
| a8 = args.src.read_u8?() |
| if (a8 == 1) or (a8 == 5) or (a8 > 6) { |
| return "#bad header" |
| } |
| this.color_type = a8 |
| |
| // Compression. |
| a8 = args.src.read_u8?() |
| if a8 <> 0 { |
| return "#bad header" |
| } |
| |
| // Filter. |
| a8 = args.src.read_u8?() |
| if a8 <> 0 { |
| return "#bad header" |
| } |
| |
| // Interlace. |
| a8 = args.src.read_u8?() |
| if a8 == 0 { |
| this.interlace_pass = 0 |
| } else if a8 == 1 { |
| this.interlace_pass = 1 |
| choose filter_and_swizzle = [filter_and_swizzle_tricky] |
| } else { |
| return "#bad header" |
| } |
| |
| // Derived fields. |
| this.filter_distance = 0 |
| this.assign_filter_distance!() |
| if this.filter_distance == 0 { |
| return "#unsupported PNG file" |
| } |
| this.overall_workbuf_length = (this.height as base.u64) * |
| (1 + this.calculate_bytes_per_row(width: this.width)) |
| this.choose_filter_implementations!() |
| } |
| |
| pri func decoder.assign_filter_distance!() { |
| if this.depth < 8 { |
| if this.color_type == 0 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__Y |
| this.src_pixfmt = base.PIXEL_FORMAT__Y |
| } else if this.color_type == 3 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__INDEXED__BGRA_BINARY |
| this.src_pixfmt = base.PIXEL_FORMAT__INDEXED__BGRA_BINARY |
| } else { |
| return nothing |
| } |
| |
| this.filter_distance = 1 |
| choose filter_and_swizzle = [filter_and_swizzle_tricky] |
| |
| } else if this.color_type == 0 { |
| if this.depth == 8 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__Y |
| this.src_pixfmt = base.PIXEL_FORMAT__Y |
| this.filter_distance = 1 |
| } else if this.depth == 16 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__Y_16LE |
| this.src_pixfmt = base.PIXEL_FORMAT__Y_16BE |
| this.filter_distance = 2 |
| } |
| |
| } else if this.color_type == 2 { |
| if this.depth == 8 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGR |
| this.src_pixfmt = base.PIXEL_FORMAT__RGB |
| this.filter_distance = 3 |
| } else if this.depth == 16 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| this.src_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| this.filter_distance = 6 |
| choose filter_and_swizzle = [filter_and_swizzle_tricky] |
| } |
| |
| } else if this.color_type == 3 { |
| if this.depth == 8 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__INDEXED__BGRA_BINARY |
| this.src_pixfmt = base.PIXEL_FORMAT__INDEXED__BGRA_BINARY |
| this.filter_distance = 1 |
| } |
| |
| } else if this.color_type == 4 { |
| if this.depth == 8 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL |
| this.src_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL |
| this.filter_distance = 2 |
| choose filter_and_swizzle = [filter_and_swizzle_tricky] |
| } else if this.depth == 16 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| this.src_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| this.filter_distance = 4 |
| choose filter_and_swizzle = [filter_and_swizzle_tricky] |
| } |
| |
| } else if this.color_type == 6 { |
| if this.depth == 8 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL |
| this.src_pixfmt = base.PIXEL_FORMAT__RGBA_NONPREMUL |
| this.filter_distance = 4 |
| } else if this.depth == 16 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| this.src_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| this.filter_distance = 8 |
| choose filter_and_swizzle = [filter_and_swizzle_tricky] |
| } |
| } |
| } |
| |
| pri func decoder.calculate_bytes_per_row(width: base.u32[..= 0x00FF_FFFF]) base.u64[..= 0x07FF_FFF8] { |
| var bytes_per_channel : base.u64[..= 2] |
| |
| if this.depth == 1 { |
| return ((args.width + 7) / 8) as base.u64 |
| } else if this.depth == 2 { |
| return ((args.width + 3) / 4) as base.u64 |
| } else if this.depth == 4 { |
| return ((args.width + 1) / 2) as base.u64 |
| } |
| bytes_per_channel = (this.depth >> 3) as base.u64 |
| return (args.width as base.u64) * bytes_per_channel * |
| (NUM_CHANNELS[this.color_type] as base.u64) |
| } |
| |
| pri func decoder.choose_filter_implementations!() { |
| // Filter 0 is a no-op. Filter 2, the up filter, should already vectorize |
| // easily by a good optimizing C compiler. |
| if this.filter_distance == 3 { |
| choose filter_1 = [filter_1_distance_3_fallback] |
| choose filter_3 = [filter_3_distance_3_fallback] |
| choose filter_4 = [ |
| filter_4_distance_3_arm_neon, |
| filter_4_distance_3_x86_sse42, |
| filter_4_distance_3_fallback] |
| } else if this.filter_distance == 4 { |
| choose filter_1 = [ |
| filter_1_distance_4_arm_neon, |
| filter_1_distance_4_x86_sse42, |
| filter_1_distance_4_fallback] |
| choose filter_3 = [ |
| filter_3_distance_4_arm_neon, |
| filter_3_distance_4_x86_sse42, |
| filter_3_distance_4_fallback] |
| choose filter_4 = [ |
| filter_4_distance_4_arm_neon, |
| filter_4_distance_4_x86_sse42, |
| filter_4_distance_4_fallback] |
| } |
| } |
| |
| pri func decoder.decode_other_chunk?(src: base.io_reader) { |
| if this.chunk_type == 'PLTE'le { |
| if this.seen_plte or (this.color_type <> 3) { |
| return "#bad chunk" |
| } |
| this.decode_plte?(src: args.src) |
| this.seen_plte = true |
| } else if this.chunk_type == 'tRNS'le { |
| if this.seen_trns or (this.color_type > 3) or |
| ((this.color_type == 3) and (not this.seen_plte)) { |
| return "#bad chunk" |
| } |
| this.decode_trns?(src: args.src) |
| this.seen_trns = true |
| } else { |
| args.src.skip?(n: this.chunk_length) |
| } |
| } |
| |
| pri func decoder.decode_plte?(src: base.io_reader) { |
| var num_entries : base.u32[..= 256] |
| var i : base.u32 |
| var argb : base.u32 |
| |
| if (this.chunk_length > 768) or ((this.chunk_length % 3) <> 0) { |
| return "#bad chunk" |
| } |
| num_entries = (this.chunk_length as base.u32) / 3 |
| |
| while i < num_entries { |
| assert i < 256 via "a < b: a < c; c <= b"(c: num_entries) |
| // Convert from RGB (in memory order) to ARGB (in native u32 order) |
| // to BGRA (in memory order). |
| argb = args.src.read_u24be_as_u32?() |
| argb |= 0xFF00_0000 |
| this.src_palette[(4 * i) + 0] = ((argb >> 0) & 0xFF) as base.u8 |
| this.src_palette[(4 * i) + 1] = ((argb >> 8) & 0xFF) as base.u8 |
| this.src_palette[(4 * i) + 2] = ((argb >> 16) & 0xFF) as base.u8 |
| this.src_palette[(4 * i) + 3] = ((argb >> 24) & 0xFF) as base.u8 |
| i += 1 |
| } endwhile |
| |
| // Set the remaining palette entries to opaque black. |
| while i < 256 { |
| this.src_palette[(4 * i) + 0] = 0x00 |
| this.src_palette[(4 * i) + 1] = 0x00 |
| this.src_palette[(4 * i) + 2] = 0x00 |
| this.src_palette[(4 * i) + 3] = 0xFF |
| i += 1 |
| } endwhile |
| } |
| |
| pri func decoder.decode_trns?(src: base.io_reader) { |
| var num_entries : base.u32[..= 256] |
| var i : base.u32 |
| |
| if this.chunk_length > 256 { |
| return "#bad chunk" |
| } |
| num_entries = this.chunk_length as base.u32 |
| |
| while i < num_entries { |
| assert i < 256 via "a < b: a < c; c <= b"(c: num_entries) |
| this.src_palette[(4 * i) + 3] = args.src.read_u8?() |
| i += 1 |
| } endwhile |
| |
| if this.color_type == 3 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__INDEXED__BGRA_NONPREMUL |
| this.src_pixfmt = base.PIXEL_FORMAT__INDEXED__BGRA_NONPREMUL |
| } else { |
| choose filter_and_swizzle = [filter_and_swizzle_tricky] |
| if this.color_type == 0 { |
| // TODO: PIXEL_FORMAT__YA_NONPREMUL |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL |
| this.src_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| } else if this.color_type == 2 { |
| this.dst_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL |
| this.src_pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE |
| } |
| } |
| } |
| |
| pub func decoder.decode_frame_config?(dst: nptr base.frame_config, src: base.io_reader) { |
| if this.call_sequence < 3 { |
| this.decode_image_config?(dst: nullptr, src: args.src) |
| } else if this.call_sequence == 3 { |
| if this.frame_config_io_position <> args.src.position() { |
| return base."#bad restart" |
| } |
| } else if this.call_sequence == 4 { |
| this.call_sequence = 0xFF |
| 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: this.frame_config_io_position, |
| disposal: 0, |
| opaque_within_bounds: false, |
| overwrite_instead_of_blend: false, |
| background_color: 0x0000_0000) |
| } |
| |
| this.call_sequence = 4 |
| } |
| |
| 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 |
| var pass_width : base.u32[..= 0x00FF_FFFF] |
| var pass_height : base.u32[..= 0x00FF_FFFF] |
| |
| if this.call_sequence < 4 { |
| this.decode_frame_config?(dst: nullptr, src: args.src) |
| } else if this.call_sequence == 4 { |
| // No-op. |
| } else { |
| return base."@end of data" |
| } |
| |
| status = this.swizzler.prepare!( |
| dst_pixfmt: args.dst.pixel_format(), |
| dst_palette: args.dst.palette_or_else(fallback: this.dst_palette[..]), |
| src_pixfmt: this.util.make_pixel_format(repr: this.src_pixfmt), |
| src_palette: this.src_palette[..], |
| blend: args.blend) |
| if not status.is_ok() { |
| return status |
| } |
| |
| while true { |
| pass_width = 0x00FF_FFFF & |
| (((INTERLACING[this.interlace_pass][1] as base.u32) + this.width) >> |
| INTERLACING[this.interlace_pass][0]) |
| pass_height = 0x00FF_FFFF & |
| (((INTERLACING[this.interlace_pass][4] as base.u32) + this.height) >> |
| INTERLACING[this.interlace_pass][3]) |
| |
| if (pass_width > 0) and (pass_height > 0) { |
| this.pass_bytes_per_row = this.calculate_bytes_per_row(width: pass_width) |
| this.pass_workbuf_length = (pass_height as base.u64) * (1 + this.pass_bytes_per_row) |
| this.decode_pass?(src: args.src, workbuf: args.workbuf) |
| status = this.filter_and_swizzle!(dst: args.dst, workbuf: args.workbuf) |
| if not status.is_ok() { |
| return status |
| } |
| } |
| |
| if (this.interlace_pass == 0) or (this.interlace_pass >= 7) { |
| break |
| } |
| this.interlace_pass += 1 |
| } endwhile |
| |
| this.call_sequence = 0xFF |
| } |
| |
| pri func decoder.decode_pass?(src: base.io_reader, workbuf: slice base.u8) { |
| var w : base.io_writer |
| var w_mark : base.u64 |
| var r_mark : base.u64 |
| var zlib_status : base.status |
| var checksum_have : base.u32 |
| var checksum_want : base.u32 |
| |
| this.workbuf_wi = 0 |
| while true { |
| if (this.workbuf_wi > this.pass_workbuf_length) or ( |
| this.pass_workbuf_length > args.workbuf.length()) { |
| return base."#bad workbuf length" |
| } |
| io_bind (io: w, data: args.workbuf[this.workbuf_wi .. this.pass_workbuf_length]) { |
| io_limit (io: args.src, limit: this.chunk_length) { |
| w_mark = w.mark() |
| r_mark = args.src.mark() |
| zlib_status =? this.zlib.transform_io?( |
| dst: w, src: args.src, workbuf: this.util.empty_slice_u8()) |
| if not this.ignore_checksum { |
| this.crc32.update_u32!(x: args.src.since(mark: r_mark)) |
| } |
| this.chunk_length ~sat-= args.src.count_since(mark: r_mark) |
| this.workbuf_wi ~sat+= w.count_since(mark: w_mark) |
| } |
| } |
| |
| if zlib_status.is_ok() { |
| // Verify the final IDAT chunk's CRC-32 checksum. |
| if not this.ignore_checksum { |
| if this.chunk_length > 0 { |
| // TODO: should this really be a fatal error? |
| return base."#too much data" |
| } |
| checksum_have = this.crc32.update_u32!(x: this.util.empty_slice_u8()) |
| checksum_want = args.src.read_u32be?() |
| if checksum_have <> checksum_want { |
| return "#bad checksum" |
| } |
| } |
| break |
| } else if zlib_status == base."$short write" { |
| if (1 <= this.interlace_pass) and (this.interlace_pass <= 6) { |
| break |
| } |
| return base."#too much data" |
| } else if zlib_status <> base."$short read" { |
| return zlib_status |
| } else if this.chunk_length == 0 { |
| // Verify the non-final IDAT chunk's CRC-32 checksum. |
| checksum_want = args.src.read_u32be?() |
| if not this.ignore_checksum { |
| checksum_have = this.crc32.update_u32!(x: this.util.empty_slice_u8()) |
| if checksum_have <> checksum_want { |
| return "#bad checksum" |
| } |
| } |
| |
| // The next chunk should be another IDAT. |
| this.chunk_length = args.src.read_u32be_as_u64?() |
| this.chunk_type = args.src.read_u32le?() |
| if this.chunk_type <> 'IDAT'le { |
| return "#bad chunk" |
| } |
| |
| // The 'IDAT'be is part of the next CRC-32 checksum's input. |
| if not this.ignore_checksum { |
| this.crc32.reset!() |
| this.chunk_type_array[0] = 'I' |
| this.chunk_type_array[1] = 'D' |
| this.chunk_type_array[2] = 'A' |
| this.chunk_type_array[3] = 'T' |
| this.crc32.update_u32!(x: this.chunk_type_array[..]) |
| } |
| continue |
| } else if args.src.length() > 0 { |
| return "#internal error: zlib decoder did not exhaust its input" |
| } |
| yield? base."$short read" |
| } endwhile |
| |
| if this.workbuf_wi <> this.pass_workbuf_length { |
| return base."#not enough data" |
| } else if 0 < args.workbuf.length() { |
| // For the top row, the Paeth filter (4) is equivalent to the Sub |
| // filter (1), but the Paeth implementation is simpler if it can assume |
| // that there is a previous row. |
| if args.workbuf[0] == 4 { |
| args.workbuf[0] = 1 |
| } |
| } |
| } |
| |
| 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 > 3 { |
| return 1 |
| } |
| return 0 |
| } |
| |
| pub func decoder.num_decoded_frames() base.u64 { |
| if this.call_sequence > 4 { |
| return 1 |
| } |
| return 0 |
| } |
| |
| pub func decoder.restart_frame!(index: base.u64, io_position: base.u64) base.status { |
| if this.call_sequence < 3 { |
| return base."#bad call sequence" |
| } |
| if args.index <> 0 { |
| return base."#bad argument" |
| } |
| this.call_sequence = 3 |
| if this.interlace_pass >= 1 { |
| this.interlace_pass = 1 |
| } |
| this.frame_config_io_position = args.io_position |
| return ok |
| } |
| |
| pub func decoder.set_report_metadata!(fourcc: base.u32, report: base.bool) { |
| // TODO. |
| } |
| |
| 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: this.overall_workbuf_length, |
| max_incl: this.overall_workbuf_length) |
| } |
| |
| // INTERLACING holds the Adam7 interlacing pattern, involving 7 passes: |
| // 1 6 4 6 2 6 4 6 |
| // 7 7 7 7 7 7 7 7 |
| // 5 6 5 6 5 6 5 6 |
| // 7 7 7 7 7 7 7 7 |
| // 3 6 4 6 3 6 4 6 |
| // 7 7 7 7 7 7 7 7 |
| // 5 6 5 6 5 6 5 6 |
| // 7 7 7 7 7 7 7 7 |
| // |
| // The six elements of each inner array are: |
| // 0: log2(x_stride) |
| // 1: x_stride - x_offset - 1 |
| // 2: x_offset |
| // 3: log2(y_stride) |
| // 4: y_stride - y_offset - 1 |
| // 5: y_offset |
| pri const INTERLACING : array[8] array[6] base.u8[..= 8] = [ |
| [0, 0, 0, 0, 0, 0], // non-interlaced; xy_stride=1, xy_offset=0 |
| [3, 7, 0, 3, 7, 0], // interlace_pass == 1 |
| [3, 3, 4, 3, 7, 0], // interlace_pass == 2 |
| [2, 3, 0, 3, 3, 4], // interlace_pass == 3 |
| [2, 1, 2, 2, 3, 0], // interlace_pass == 4 |
| [1, 1, 0, 2, 1, 2], // interlace_pass == 5 |
| [1, 0, 1, 1, 1, 0], // interlace_pass == 6 |
| [0, 0, 0, 1, 0, 1], // interlace_pass == 7 |
| ] |
| |
| // LOW_BIT_DEPTH_MULTIPLIERS holds multipliers that convert D-bit values into |
| // 8-bit values, for depth D. |
| pri const LOW_BIT_DEPTH_MULTIPLIERS : array[8] base.u8 = [ |
| 0, |
| 0b1111_1111, // depth == 1 |
| 0b0101_0101, // depth == 2 |
| 0, |
| 0b0001_0001, // depth == 4 |
| 0, |
| 0, |
| 0, |
| ] |
| |
| // LOW_BIT_DEPTH_NUM_PACKS holds the number of smaller-than-1-byte units that |
| // are packed into each byte. |
| pri const LOW_BIT_DEPTH_NUM_PACKS : array[8] base.u8 = [ |
| 0, |
| 8, // depth == 1 |
| 4, // depth == 2 |
| 0, |
| 2, // depth == 4 |
| 0, |
| 0, |
| 0, |
| ] |
| |
| // NUM_CHANNELS holds the number of channels for each valid color type. |
| pri const NUM_CHANNELS : array[8] base.u8[..= 4] = [ |
| 1, // color_type == 0: Y |
| 0, |
| 3, // color_type == 2: RGB |
| 1, // color_type == 3: indexed |
| 2, // color_type == 4: YA |
| 0, |
| 4, // color_type == 6: RGBA |
| 0, |
| ] |