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// 纯 MoonBit 图像缩放（全目标可用：native/wasm/js）
// 仅依赖 @types，不依赖 @core/FFI
// 支持最近邻 + 双线性插值
///|
/// 双线性插值采样。在 (x, y) 处采样通道 c 的值。
fn resize_sample_bilinear(
data : Array[Int],
w : Int,
h : Int,
ch : Int,
c : Int,
x : Float,
y : Float,
) -> Int {
let x0 = x.to_int()
let y0 = y.to_int()
let w_minus_1 = w - 1
let h_minus_1 = h - 1
let x0c = x0.clamp(min=0, max=w_minus_1)
let y0c = y0.clamp(min=0, max=h_minus_1)
let x1 = (x0 + 1).clamp(min=0, max=w_minus_1)
let y1 = (y0 + 1).clamp(min=0, max=h_minus_1)
let fx = x - Float::from_int(x0)
let fy = y - Float::from_int(y0)
let p00 = data[(y0c * w + x0c) * ch + c]
let p10 = data[(y0c * w + x1) * ch + c]
let p01 = data[(y1 * w + x0c) * ch + c]
let p11 = data[(y1 * w + x1) * ch + c]
let top = Float::from_int(p00) * (1.0F - fx) + Float::from_int(p10) * fx
let bot = Float::from_int(p01) * (1.0F - fx) + Float::from_int(p11) * fx
(top * (1.0F - fy) + bot * fy + 0.5F).to_int()
}
///|
/// 最近邻采样。在 (x, y) 处采样通道 c 的值。
fn resize_sample_nearest(
data : Array[Int],
w : Int,
h : Int,
ch : Int,
c : Int,
x : Float,
y : Float,
) -> Int {
let xi = (x + 0.5F).to_int().clamp(min=0, max=w - 1)
let yi = (y + 0.5F).to_int().clamp(min=0, max=h - 1)
data[(yi * w + xi) * ch + c]
}
///|
/// resize 8-bit 图像（纯 MoonBit，全目标可用）。
/// 使用双线性插值（filter = PointSample 时使用最近邻）。
/// edge 参数目前统一按 Clamp 处理（边缘像素重复）。
pub fn resize_pure(
img : @types.Image,
out_w : Int,
out_h : Int,
filter? : @types.ResizeFilter = @types.ResizeFilter::Default,
edge? : @types.ResizeEdge = @types.ResizeEdge::Clamp,
) -> @types.Image raise @types.LoadError {
let _ = edge
if out_w <= 0 || out_h <= 0 {
raise @types.LoadError::DecodeFailed("resize 输出尺寸必须为正数")
}
let ch = img.channels
let w = img.width
let h = img.height
let data_int : Array[Int] = Array::make(w * h * ch, 0)
for i in 0..<(w * h * ch) {
data_int[i] = img.data[i].to_int()
}
let scale_x = Float::from_int(w) / Float::from_int(out_w)
let scale_y = Float::from_int(h) / Float::from_int(out_h)
let use_nearest = match filter {
PointSample => true
_ => false
}
let out : Array[Byte] = Array::make(out_w * out_h * ch, b'\x00')
for dy in 0..<out_h {
let sy = (Float::from_int(dy) + 0.5F) * scale_y - 0.5F
for dx in 0..<out_w {
let sx = (Float::from_int(dx) + 0.5F) * scale_x - 0.5F
for ci in 0..<ch {
let val = if use_nearest {
resize_sample_nearest(data_int, w, h, ch, ci, sx, sy)
} else {
resize_sample_bilinear(data_int, w, h, ch, ci, sx, sy)
}
out[(dy * out_w + dx) * ch + ci] = val.clamp(min=0, max=255).to_byte()
}
}
}
@types.Image::{
width: out_w,
height: out_h,
channels: ch,
data: Bytes::from_array(out),
}
}