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|
const std = @import("std");
const Allocator = std.mem.Allocator;
const assert = std.debug.assert;
const c = @import("wuffs_c");
const Error = @import("error.zig").Error;
const log = std.log.scoped(.wuffs_swizzler);
pub fn gToRgba(alloc: Allocator, src: []const u8) Error![]u8 {
return swizzle(
alloc,
src,
c.WUFFS_BASE__PIXEL_FORMAT__Y,
c.WUFFS_BASE__PIXEL_FORMAT__RGBA_PREMUL,
);
}
pub fn gaToRgba(alloc: Allocator, src: []const u8) Error![]u8 {
// Wuffs doesn't support YA_PREMUL as a swizzle source. The nonpremul
// pair produces the same bytes (r=g=b=y, a=a, no alpha math), which
// is what we want: alpha semantics are preserved as-is, matching the
// other conversions here.
return swizzle(
alloc,
src,
c.WUFFS_BASE__PIXEL_FORMAT__YA_NONPREMUL,
c.WUFFS_BASE__PIXEL_FORMAT__RGBA_NONPREMUL,
);
}
pub fn rgbToRgba(alloc: Allocator, src: []const u8) Error![]u8 {
return swizzle(
alloc,
src,
c.WUFFS_BASE__PIXEL_FORMAT__RGB,
c.WUFFS_BASE__PIXEL_FORMAT__RGBA_PREMUL,
);
}
pub fn bgrToRgba(alloc: Allocator, src: []const u8) Error![]u8 {
return swizzle(
alloc,
src,
c.WUFFS_BASE__PIXEL_FORMAT__BGR,
c.WUFFS_BASE__PIXEL_FORMAT__RGBA_PREMUL,
);
}
pub fn bgraToRgba(alloc: Allocator, src: []const u8) Error![]u8 {
return swizzle(
alloc,
src,
c.WUFFS_BASE__PIXEL_FORMAT__BGRA_PREMUL,
c.WUFFS_BASE__PIXEL_FORMAT__RGBA_PREMUL,
);
}
/// Composite `src` over `dst` in place. Both are straight
/// (non-premultiplied) alpha RGBA of the same length. A transparent
/// destination pixel takes the source pixel exactly; wuffs composites
/// everything else in 16-bit integer space.
pub fn rgbaSrcOver(dst: []u8, src: []const u8) void {
assert(dst.len == src.len);
assert(dst.len % 4 == 0);
var swizzler: c.wuffs_base__pixel_swizzler = undefined;
const status = c.wuffs_base__pixel_swizzler__prepare(
&swizzler,
c.wuffs_base__make_pixel_format(c.WUFFS_BASE__PIXEL_FORMAT__RGBA_NONPREMUL),
c.wuffs_base__empty_slice_u8(),
c.wuffs_base__make_pixel_format(c.WUFFS_BASE__PIXEL_FORMAT__RGBA_NONPREMUL),
c.wuffs_base__empty_slice_u8(),
c.WUFFS_BASE__PIXEL_BLEND__SRC_OVER,
);
// This format pair and blend mode is a supported swizzle, so
// preparation can only fail on a programming error.
assert(c.wuffs_base__status__is_ok(&status));
_ = c.wuffs_base__pixel_swizzler__swizzle_interleaved_from_slice(
&swizzler,
c.wuffs_base__make_slice_u8(dst.ptr, dst.len),
c.wuffs_base__empty_slice_u8(),
c.wuffs_base__make_slice_u8(@constCast(src.ptr), src.len),
);
}
test "gaToRgba" {
const rgba = try gaToRgba(std.testing.allocator, &.{ 7, 100, 8, 200 });
defer std.testing.allocator.free(rgba);
try std.testing.expectEqualSlices(u8, &.{
7, 7, 7, 100,
8, 8, 8, 200,
}, rgba);
}
test "rgbaSrcOver" {
// 50% white over opaque black, opaque over anything, transparent
// source over anything, and anything over a transparent
// destination (exact source passthrough).
var dst = [_]u8{
0, 0, 0, 255,
10, 20, 30, 40,
10, 20, 30, 40,
0, 0, 0, 0,
};
rgbaSrcOver(&dst, &.{
255, 255, 255, 128,
100, 110, 120, 255,
100, 110, 120, 0,
200, 100, 50, 128,
});
try std.testing.expectEqualSlices(u8, &.{
128, 128, 128, 255,
100, 110, 120, 255,
10, 20, 30, 40,
200, 100, 50, 128,
}, &dst);
}
fn swizzle(
alloc: Allocator,
src: []const u8,
comptime src_pixel_format: u32,
comptime dst_pixel_format: u32,
) Error![]u8 {
const src_slice = c.wuffs_base__make_slice_u8(
@constCast(src.ptr),
src.len,
);
const dst_fmt = c.wuffs_base__make_pixel_format(
dst_pixel_format,
);
assert(c.wuffs_base__pixel_format__is_direct(&dst_fmt));
assert(c.wuffs_base__pixel_format__is_interleaved(&dst_fmt));
assert(c.wuffs_base__pixel_format__bits_per_pixel(&dst_fmt) % 8 == 0);
const dst_size = c.wuffs_base__pixel_format__bits_per_pixel(&dst_fmt) / 8;
const src_fmt = c.wuffs_base__make_pixel_format(
src_pixel_format,
);
assert(c.wuffs_base__pixel_format__is_direct(&src_fmt));
assert(c.wuffs_base__pixel_format__is_interleaved(&src_fmt));
assert(c.wuffs_base__pixel_format__bits_per_pixel(&src_fmt) % 8 == 0);
const src_size = c.wuffs_base__pixel_format__bits_per_pixel(&src_fmt) / 8;
assert(src.len % src_size == 0);
const dst = try alloc.alloc(u8, src.len * dst_size / src_size);
errdefer alloc.free(dst);
const dst_slice = c.wuffs_base__make_slice_u8(
dst.ptr,
dst.len,
);
var swizzler: c.wuffs_base__pixel_swizzler = undefined;
{
const status = c.wuffs_base__pixel_swizzler__prepare(
&swizzler,
dst_fmt,
c.wuffs_base__empty_slice_u8(),
src_fmt,
c.wuffs_base__empty_slice_u8(),
c.WUFFS_BASE__PIXEL_BLEND__SRC,
);
if (!c.wuffs_base__status__is_ok(&status)) {
const e = c.wuffs_base__status__message(&status);
log.warn("{s}", .{e});
return error.WuffsError;
}
}
{
_ = c.wuffs_base__pixel_swizzler__swizzle_interleaved_from_slice(
&swizzler,
dst_slice,
c.wuffs_base__empty_slice_u8(),
src_slice,
);
}
return dst;
}
|
