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Module overlay

blittle

Module overlay 

Source
Available on crate feature overlay only.
Expand description

This module contains functions for overlaying a source image onto destination image using alpha (transparency) value(s).

To overlay one pixel onto another, the pixels must be converted from three to four 1-byte channels to four 4-byte channels. For example, RGB8 must be converted into RGBA32 (where the value of each channel ranges from 0.0 to 1.0). In this module, blittle uses Vec4 to represent an RGBA32 pixel. This allows blittle to use glam’s SIMD magic.

As always, it is more efficient to pre-allocate your Vec<Vec4> outputs if you intend to overlay more than once. For example: rgb8_to_rgba32 returns a Vec<Vec4> representation of the src image, but it would be faster to pre-allocate instead and then call rgb8_to_rgba32_in_place:

use blittle::overlay::{rgb8_to_rgba32_in_place, Vec4};
use blittle::stride::RGB;

let w = 16;
let h = 16;
let src = vec![200; w * h * RGB];
let mut dst = vec![Vec4::default(); w * h];
rgb8_to_rgba32_in_place(&src, &mut dst);

Likewise, it’s faster to pre-allocate and then perform the actual overlaying operation:

use blittle::overlay::*;
use blittle::{ClippedRect, PositionI, Size};
use blittle::stride::{RGB, RGBA};


let w = 16;
let h = 16;

let src8 = vec![200; w * h * RGB];
// Convert src to RGBA32.
let mut src32 = vec![Vec4::default(); w * h];
rgb8_to_rgba32_in_place(&src8, &mut src32);

let mut dst8 = vec![90; w * h * RGBA];
/// Convert dst to RGBA32.
let mut dst32 = vec![Vec4::default(); w * h];
rgba8_to_rgba32_in_place(&dst8, &mut dst32);

// Overlay src onto dst.
let size = Size { w, h };
let position = PositionI::default();
let rect = ClippedRect::new(PositionI::default(), size, size).unwrap();
overlay_rgba32(&src32, &mut dst32, &rect);

// Convert dst32 back into RGBA8.
rgba32_to_rgba8_in_place(&dst32, &mut dst8);

Structs§

Vec4
A 4-dimensional vector.

Functions§

overlay_pixel
Overlay a src pixel onto a dst pixel.
overlay_rgb8
Overlay src onto dst using an alpha value.
overlay_rgba8
Overlay src onto dst.
overlay_rgba32
Overlay src onto dst.
rgb8_to_rgba32
Convert a bitmap of RGB8 pixels (1 byte per channel) into a slice of Vec4.
rgb8_to_rgba32_color
Convert an RGB8 color to an RGBA32 color.
rgb8_to_rgba32_in_place
Convert a bitmap of RGB8 pixels (1 byte per channel) into a slice of Vec4.
rgba8_to_rgba32
Convert a bitmap of RGBA8 pixels (1 byte per channel) into a slice of Vec4.
rgba8_to_rgba32_color
Convert an RGB8 color to an RGBA32 color.
rgba8_to_rgba32_in_place
Convert a bitmap of RGBA8 pixels (1 byte per channel) into a slice of Vec4.
rgba32_to_rgb8
Convert a bitmap of RGB32 pixels (4 bytes per channel) into a raw RGB8 byte slice.
rgba32_to_rgb8_color
Convert an RGBA32 color to an RGB8 color.
rgba32_to_rgb8_in_place
Convert a bitmap of RGB32 pixels (4 bytes per channel) into a raw RGB8 byte slice.
rgba32_to_rgba8
Convert a bitmap of RGBA32 pixels (4 bytes per channel) into a raw RGBA byte slice.
rgba32_to_rgba8_color
Convert an RGBA32 color to an RGBA8 color.
rgba32_to_rgba8_in_place
Convert a bitmap of RGBA32 pixels (4 bytes per channel) into a raw RGBA byte slice.