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// 伪彩色映射（纯 MoonBit）：apply_colormap + 预设色彩映射表
///|
/// 色彩映射预设
pub(all) enum Colormap {
JET // 蓝→青→绿→黄→红
HOT // 黑→红→黄→白
COOL // 青→品红
GRAY // 灰度
BONE // 偏蓝灰
COPPER // 偏铜色
}
///|
fn get_colormap_lut(map : Colormap) -> Array[(Byte, Byte, Byte)] {
let lut : Array[(Byte, Byte, Byte)] = Array::make(
256,
(b'\x00', b'\x00', b'\x00'),
)
for i in 0..<256 {
let t = Float::from_int(i) / 255.0F
let (r, g, b) = match map {
JET => {
// JET: 4 段线性插值
let r_val = if t < 0.375F {
0.0F
} else if t < 0.625F {
(t - 0.375F) / 0.25F
} else {
1.0F
}
let g_val = if t < 0.125F {
0.0F
} else if t < 0.375F {
(t - 0.125F) / 0.25F
} else if t < 0.625F {
1.0F
} else if t < 0.875F {
1.0F - (t - 0.625F) / 0.25F
} else {
0.0F
}
let b_val = if t < 0.125F {
0.5F + t / 0.25F * 0.5F
} else if t < 0.375F {
1.0F
} else if t < 0.625F {
1.0F - (t - 0.375F) / 0.25F
} else {
0.0F
}
(r_val, g_val, b_val)
}
HOT => {
let r_val = if t < 0.333F { t / 0.333F } else { 1.0F }
let g_val = if t < 0.333F {
0.0F
} else if t < 0.666F {
(t - 0.333F) / 0.333F
} else {
1.0F
}
let b_val = if t < 0.666F { 0.0F } else { (t - 0.666F) / 0.334F }
(r_val, g_val, b_val)
}
COOL => (0.0F, t, 1.0F - t)
GRAY => (t, t, t)
BONE =>
// 偏蓝灰
(t * 0.93F, t * 0.88F, t * 1.0F)
COPPER =>
// 偏铜色
((t * 1.25F).clamp(min=0.0F, max=1.0F), t * 0.78F, t * 0.5F)
}
lut[i] = (
(r * 255.0F + 0.5F).to_int().clamp(min=0, max=255).to_byte(),
(g * 255.0F + 0.5F).to_int().clamp(min=0, max=255).to_byte(),
(b * 255.0F + 0.5F).to_int().clamp(min=0, max=255).to_byte(),
)
}
lut
}
///|
/// 伪彩色映射。将灰度图或彩色图（先转灰度）映射为 RGB 伪彩色图像。
pub fn apply_colormap(
img : @types.Image,
map : Colormap,
) -> @types.Image raise @types.LoadError {
// 输入验证
if img.width <= 0 || img.height <= 0 {
raise @types.LoadError::DecodeFailed(
"apply_colormap: 图像尺寸必须大于0",
)
}
if img.channels < 1 || img.channels > 4 {
raise @types.LoadError::DecodeFailed(
"apply_colormap: 通道数必须在1-4之间",
)
}
let expected_size = img.width * img.height * img.channels
if img.data.length() != expected_size {
raise @types.LoadError::DecodeFailed(
"apply_colormap: 数据大小不匹配，期望 " +
expected_size.to_string() +
"，实际 " +
img.data.length().to_string(),
)
}
let lut = get_colormap_lut(map)
let n = img.width * img.height
let ch = img.channels
let out : Array[Byte] = Array::make(n * 3, b'\x00')
for i in 0..<n {
let gray = if ch == 1 {
img.data[i].to_int()
} else {
let r = img.data[i * ch].to_int()
let g = img.data[i * ch + 1].to_int()
let b = img.data[i * ch + 2].to_int()
(r * 299 + g * 587 + b * 114) / 1000
}
let (cr, cg, cb) = lut[gray]
out[i * 3] = cr
out[i * 3 + 1] = cg
out[i * 3 + 2] = cb
}
@types.Image::{
width: img.width,
height: img.height,
channels: 3,
data: Bytes::from_array(out),
}
}