PixMap.SetPixel alternative

[adamsanclemente]

I would like there to be a way to use precomputed colors in PixMap.SetPixel(). Every time you run it, it calls clamp() 4x. I want a way to do this computation on a set list of colors and just directly pull from there so I avoid the overhead at runtime.

So we would directly input 4x uint8s possibly stored in a struct with a conversion function.

[kolkov]

Thanks for the suggestion! You're right that SetPixel() does per-pixel work (4x clamp + premultiply) that's unnecessary when you already have precomputed colors.

Good news — there's already a zero-overhead path available today via Data():

data := pixmap.Data()
width := pixmap.Width()

// Precompute your palette once (premultiplied RGBA, uint8):
type PremulColor struct{ R, G, B, A uint8 }
red := PremulColor{255, 0, 0, 255}

// Then write directly — no clamp, no conversion:
i := (y*width + x) * 4
data[i+0] = red.R
data[i+1] = red.G
data[i+2] = red.B
data[i+3] = red.A

Data() returns the underlying []uint8 slice (premultiplied RGBA, 4 bytes per pixel), so writes go straight to the buffer with zero overhead. You skip bounds checks, clamping, and float→uint8 conversion entirely.

We'll also add a SetPixelPremul(x, y int, r, g, b, a uint8) convenience method that takes pre-converted uint8 values — it'll still do bounds checking but skip the clamp/premultiply math. Best of both worlds for the common case.