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cleaned up custom .qoi decoder
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@10aded
10aded committed Mar 14, 2024
1 parent c2b2bcd commit 305b32f
Showing 1 changed file with 42 additions and 55 deletions.
97 changes: 42 additions & 55 deletions qoi.zig
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Original file line number Diff line number Diff line change
@@ -1,19 +1,26 @@
const std = @import("std");

// The (Zig-made!) image viewer at:
// This file is just a custom .qoi image decoder; it doesn't encode .qoi images.
// There are some tests at the end, these can be run with the command
//
// zig test qoi.zig
//
// The output should be
//
// "All 3 tests passed."
//
// An individual test can be run with (e.g.) the command
//
// zig test --test-filter "RRRB decoder" .\qoi.zig
//
// While the .qoi image format is extremely simple, many image viewers (sadly)
// do not support it. E.g. the standard Windows "Photos" app.
//
// Luckily, the Zig community has come to the rescue, and there is a Zig-made
// .qoi image viewer at:
//
// https://github.com/marler8997/image-viewer
//
// is significantly better (for real) than the "Photos" app since
// it can actually render .qoi files AND allows arbitrary zoom.



const RRRB_image = @embedFile("QOI-Tests/RRRB.qoi");
const RRRBXRBBX_image = @embedFile("QOI-Tests/RRRBXRBBX.qoi");
const three_by_four_image = @embedFile("QOI-Tests/3x4.qoi");
const std = @import("std");

const dprint = std.debug.print;
const dassert = std.debug.assert;

const Pixel = [4] u8;
Expand All @@ -29,9 +36,8 @@ const Qoi_Header = struct {
// Note: In Zig DEBUG builds, static memory that are set to undefined are
// filled with 0xaa s.

pub fn comptime_header_parser( embedded_qoi_file : [] const u8) Qoi_Header {
// Parse the image header into the qoi_header struct.
const raw_image = embedded_qoi_file;
pub fn comptime_header_parser( raw_image : [] const u8) Qoi_Header {
// Parse the image header into the qoi_header struct.
const qoi_header = Qoi_Header{
.magic_bytes = [4]u8{raw_image[0], raw_image[1], raw_image[2], raw_image[3]},
.image_width = std.mem.readIntSlice(u32, raw_image[4..8], .Big), // (Thanks tw0st3p!)
Expand All @@ -47,12 +53,6 @@ pub fn comptime_header_parser( embedded_qoi_file : [] const u8) Qoi_Header {
return qoi_header;
}

// const test_image_header = comptime_header_parser(test_image);
// const test_image_width = test_image_header.image_width;
// const test_image_height = test_image_header.image_height;

//var test_image_pixels : [test_image_header.image_width * test_image_header.image_height] Pixel = undefined;

// In the enum below, the OP XYZ refers to QOI_OP_XYZ in the specification.
const QOI_OPS = enum(u8) {
RGB,
Expand All @@ -63,22 +63,26 @@ const QOI_OPS = enum(u8) {
RUN,
};

// @decision: Should this procedure take in a pixel array that is a matrix
// or a simple array... I feel like it should actually just be an array.
// TODO: Change the args here so that we don't use u64!
// @Maybe: Create a different 'layer' / calls to the header parser ???
// @Future
// Loading images as textures in Raylib, using this code, requires a lot of lines.
// There should be an easier of setting up the stuff in this file to reduce overhead.
// Figure this out!

pub fn qoi_to_pixels( embedded_qoi_file : [] const u8, comptime number_of_pixels : u64, pixel_array : *[number_of_pixels] Pixel ) void {
// Per the specification,
// "The decoder and encoder start with {r: 0, g: 0, b: 0, a: 255} as the
//previous pixel value."
// "The decoder and encoder start with {r: 0, g: 0, b: 0, a: 255} as the
// previous pixel value."
var current_pixel = Pixel{0,0,0,255};

// @question: Does Zig zero-init arrays by default?

// Per the specification,
// "A running array[64] (zero-initialized) of previously seen pixel
// values is maintained by the encoder and decoder."
var previously_seen_pixels : [64] Pixel = undefined;
// @question: Where exactly in the specification does the line below come from.
previously_seen_pixels[0] = Pixel{0,0,0,0};

var current_byte_index : usize = 14;
var current_byte : u8 = undefined;
var current_byte : u8 = undefined;
var current_pixel_index : usize = 0;

var current_qoi_op : QOI_OPS = undefined;
Expand Down Expand Up @@ -212,13 +216,12 @@ pub fn qoi_to_pixels( embedded_qoi_file : [] const u8, comptime number_of_pixels
previously_seen_pixels[hash] = current_pixel;
},
}


// dprint("{any}\n", .{current_pixel}); // @debug
}
// dprint("Current OP: {any}\n", .{current_qoi_op}); // @debug
}

// Per the specification,
// "The hash function for the index is:
// index_position = (r * 3 + g * 5 + b * 7 + a * 11) % 64"
fn pixel_hash(pixel : Pixel) u6 {
const r = pixel[0];
const g = pixel[1];
Expand All @@ -230,27 +233,12 @@ fn pixel_hash(pixel : Pixel) u6 {
return hash;
}

pub fn main() void {



// TODO: Turn the following into a Zig test
// Suggestion (tw0st3p:
// test "test name" { std.testing.expectEqual(@as(u8, 69, foo())) };
// const test_pixel_hash = pixel_hash(Pixel{1,1,1,1});
// Expect: 22
// const test_pixel_hash = pixel_hash(Pixel{100,0,0,0});
// Expect: 44
// dprint("PH: {d}\n", .{test_pixel_hash}); // @debug



// qoi_to_pixels(test_image, @as(u64, test_image_width) * @as(u64, test_image_height), &test_image_pixels);

// dprint("Header: {any}\n", .{test_image_header}); // @debug
// dprint("Pixels: {any}\n", .{test_image_pixels}); // @debug
}
// Test images.
const RRRB_image = @embedFile("QOI-Tests/RRRB.qoi");
const RRRBXRBBX_image = @embedFile("QOI-Tests/RRRBXRBBX.qoi");
const three_by_four_image = @embedFile("QOI-Tests/3x4.qoi");

// Tests for the decoder.
test "RRRB decoder" {
const RRRB_header = comptime comptime_header_parser(RRRB_image);
const width = @as(u64, RRRB_header.image_width);
Expand All @@ -264,7 +252,6 @@ test "RRRB decoder" {
.{0, 0, 255, 255}};

try std.testing.expectEqual(expected_pixels, RRRB_pixels);
// dprint("Pixels: {any}\n", .{RRRB_pixels}); // @debug
}

test "RRRBXRBBX decoder" {
Expand Down

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