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// 纯 MoonBit 色彩模型转换（全目标可用：native/wasm/js）
// 仅依赖 @types，不依赖 @core/FFI
// 移植自 src/process/color/color_convert.mbt:1-162 的 5 个 8-bit Image 色彩转换函数
///|
/// 转为灰度图（channels=1，纯 MoonBit，全目标可用）
/// 使用 ITU-R BT.601 亮度公式: Y = 0.299R + 0.587G + 0.114B
pub fn to_grayscale_pure(img : @types.Image) -> @types.Image {
if img.channels == 1 {
return img
}
let pixel_count = img.width * img.height
let ch = img.channels
let data_int : Array[Int] = Array::make(pixel_count * ch, 0)
for i in 0..<(pixel_count * ch) {
data_int[i] = img.data[i].to_int()
}
let out : Array[Byte] = Array::make(pixel_count, b'\x00')
for i in 0..<pixel_count {
let r = data_int[i * ch]
let g = data_int[i * ch + 1]
let b = data_int[i * ch + 2]
let gray = (r * 299 + g * 587 + b * 114) / 1000
out[i] = gray.to_byte()
}
@types.Image::{
width: img.width,
height: img.height,
channels: 1,
data: Bytes::from_array(out),
}
}
///|
/// 去除 alpha 通道（RGBA → RGB，channels=3，纯 MoonBit，全目标可用）
pub fn to_rgb_pure(img : @types.Image) -> @types.Image {
if img.channels == 3 {
return img
}
if img.channels < 3 {
return img
}
let pixel_count = img.width * img.height
let out : Array[Byte] = Array::make(pixel_count * 3, b'\x00')
for i in 0..<pixel_count {
out[i * 3] = img.data[i * img.channels]
out[i * 3 + 1] = img.data[i * img.channels + 1]
out[i * 3 + 2] = img.data[i * img.channels + 2]
}
@types.Image::{
width: img.width,
height: img.height,
channels: 3,
data: Bytes::from_array(out),
}
}
///|
/// 添加 alpha 通道（RGB → RGBA，channels=4，alpha=255，纯 MoonBit，全目标可用）
pub fn to_rgba_pure(img : @types.Image) -> @types.Image {
if img.channels == 4 {
return img
}
let pixel_count = img.width * img.height
let out : Array[Byte] = Array::make(pixel_count * 4, b'\x00')
for i in 0..<pixel_count {
let src_ch = img.channels
out[i * 4] = img.data[i * src_ch]
out[i * 4 + 1] = if src_ch >= 2 {
img.data[i * src_ch + 1]
} else {
b'\x00'
}
out[i * 4 + 2] = if src_ch >= 3 {
img.data[i * src_ch + 2]
} else {
b'\x00'
}
out[i * 4 + 3] = b'\xFF'
}
@types.Image::{
width: img.width,
height: img.height,
channels: 4,
data: Bytes::from_array(out),
}
}
///|
/// 按 stb_image 语义转换通道数（纯 MoonBit，全目标可用）
/// - 1: 灰度（BT.601 亮度公式）
/// - 2: 灰度 + alpha（alpha=255 若源无 alpha）
/// - 3: RGB（丢弃 alpha，灰度展开为 R=G=B）
/// - 4: RGBA（alpha=255 若源无 alpha，灰度展开为 R=G=B）
pub fn convert_channels_pure(
img : @types.Image,
req_channels : Int,
) -> @types.Image raise @types.LoadError {
if req_channels == img.channels {
return img
}
let pixel_count = img.width * img.height
let src_ch = img.channels
match req_channels {
1 => to_grayscale_pure(img)
2 => {
let out : Array[Byte] = Array::make(pixel_count * 2, b'\x00')
for i in 0..<pixel_count {
let gray = if src_ch >= 3 {
let r = img.data[i * src_ch].to_int()
let g = img.data[i * src_ch + 1].to_int()
let b = img.data[i * src_ch + 2].to_int()
(r * 299 + g * 587 + b * 114) / 1000
} else {
img.data[i * src_ch].to_int()
}
let alpha = if src_ch == 2 || src_ch == 4 {
img.data[i * src_ch + src_ch - 1].to_int()
} else {
255
}
out[i * 2] = gray.to_byte()
out[i * 2 + 1] = alpha.to_byte()
}
@types.Image::{
width: img.width,
height: img.height,
channels: 2,
data: Bytes::from_array(out),
}
}
3 =>
if src_ch == 1 {
let out : Array[Byte] = Array::make(pixel_count * 3, b'\x00')
for i in 0..<pixel_count {
let v = img.data[i]
out[i * 3] = v
out[i * 3 + 1] = v
out[i * 3 + 2] = v
}
@types.Image::{
width: img.width,
height: img.height,
channels: 3,
data: Bytes::from_array(out),
}
} else {
to_rgb_pure(img)
}
4 => to_rgba_pure(img)
_ => raise @types.LoadError::DecodeFailed("不支持的 req_channels 值")
}
}
///|
/// 预乘 alpha（RGBA → RGBA premultiplied，纯 MoonBit，全目标可用）
/// 要求 channels=4
pub fn premultiply_alpha_pure(
img : @types.Image,
) -> @types.Image raise @types.LoadError {
if img.channels != 4 {
raise @types.LoadError::DecodeFailed(
"premultiply_alpha_pure 需要 channels=4 (RGBA)",
)
}
let pixel_count = img.width * img.height
let data_int : Array[Int] = Array::make(pixel_count * 4, 0)
for i in 0..<(pixel_count * 4) {
data_int[i] = img.data[i].to_int()
}
let out : Array[Byte] = Array::make(pixel_count * 4, b'\x00')
for i in 0..<pixel_count {
let r = data_int[i * 4]
let g = data_int[i * 4 + 1]
let b = data_int[i * 4 + 2]
let a = data_int[i * 4 + 3]
out[i * 4] = (r * a / 255).to_byte()
out[i * 4 + 1] = (g * a / 255).to_byte()
out[i * 4 + 2] = (b * a / 255).to_byte()
out[i * 4 + 3] = a.to_byte()
}
@types.Image::{
width: img.width,
height: img.height,
channels: 4,
data: Bytes::from_array(out),
}
}
///|
/// 反预乘 alpha（RGBA premA → RGBA unpremultiplied，纯 MoonBit，全目标可用）
/// 要求 channels=4
pub fn unpremultiply_alpha_pure(
img : @types.Image,
) -> @types.Image raise @types.LoadError {
if img.channels != 4 {
raise @types.LoadError::DecodeFailed(
"unpremultiply_alpha_pure 需要 channels=4 (RGBA)",
)
}
let pixel_count = img.width * img.height
let data_int : Array[Int] = Array::make(pixel_count * 4, 0)
for i in 0..<(pixel_count * 4) {
data_int[i] = img.data[i].to_int()
}
let out : Array[Byte] = Array::make(pixel_count * 4, b'\x00')
for i in 0..<pixel_count {
let r = data_int[i * 4]
let g = data_int[i * 4 + 1]
let b = data_int[i * 4 + 2]
let a = data_int[i * 4 + 3]
if a == 0 {
out[i * 4] = b'\x00'
out[i * 4 + 1] = b'\x00'
out[i * 4 + 2] = b'\x00'
out[i * 4 + 3] = b'\x00'
} else {
out[i * 4] = (r * 255 / a).to_byte()
out[i * 4 + 1] = (g * 255 / a).to_byte()
out[i * 4 + 2] = (b * 255 / a).to_byte()
out[i * 4 + 3] = a.to_byte()
}
}
@types.Image::{
width: img.width,
height: img.height,
channels: 4,
data: Bytes::from_array(out),
}
}