dssim-core 3.5.1

Library that measures structural similarity between images using a multi-scale variant of the SSIM algorithm.
Documentation 
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use crate::Dssim;
use rgb::{RGB8, RGBA8};
use std::ptr;

pub type DssimImage = crate::DssimImage<f32>;

/// Create new context for comparisons
#[unsafe(no_mangle)]
pub extern "C" fn dssim_new() -> *mut Dssim {
    let d = Box::new(crate::new());
    Box::into_raw(d)
}

/// Free the context
#[unsafe(no_mangle)]
pub unsafe extern "C" fn dssim_free(d: *mut Dssim) {
    if d.is_null() {
        return;
    }
    let _ = unsafe { Box::from_raw(d) };
}

/// Take sRGB RGBA pixels (non-premultiplied, alpha last) and preprocess them into image format that can be compared.
///
/// Pixels are copied. Returns NULL on error.
///
/// Call `dssim_free_image` to free memory when the image is no longer needed.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn dssim_create_image_rgba(dssim: &mut Dssim, pixels: *const u8, width: u32, height: u32) -> *mut DssimImage {
    if pixels.is_null() {
        return ptr::null_mut();
    }
    let width = width as usize;
    let height = height as usize;
    let pixels = unsafe { std::slice::from_raw_parts(pixels.cast::<RGBA8>(), width * height) };
    match dssim.create_image_rgba(pixels, width, height) {
        Some(img) => Box::into_raw(Box::new(img)),
        None => ptr::null_mut(),
    }
}

/// Take sRGB RGB pixels and preprocess them into image format that can be compared.
///
/// Pixels are copied. Returns NULL on error.
///
/// Call `dssim_free_image` to free memory when the image is no longer needed.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn dssim_create_image_rgb(dssim: &mut Dssim, pixels: *const u8, width: u32, height: u32) -> *mut DssimImage {
    if pixels.is_null() {
        return ptr::null_mut();
    }
    let width = width as usize;
    let height = height as usize;
    let pixels = unsafe { std::slice::from_raw_parts(pixels.cast::<RGB8>(), width * height) };
    match dssim.create_image_rgb(pixels, width, height) {
        Some(img) => Box::into_raw(Box::new(img)),
        None => ptr::null_mut(),
    }
}

/// Free image data
#[unsafe(no_mangle)]
pub unsafe extern "C" fn dssim_free_image(img: *mut DssimImage) {
    if img.is_null() {
        return;
    }
    let _ = unsafe { Box::from_raw(img) };
}

/// Compare these two images.
///
/// `img1` can be reused for multiple comparisons.
///
/// Don't forget to free the images and the DSSIM context when done.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn dssim_compare(dssim: &mut Dssim, img1: *const DssimImage, img2: *const DssimImage) -> f64 {
    let Some(img1) = (unsafe { img1.as_ref() }) else { return f64::NAN };
    let Some(img2) = (unsafe { img2.as_ref() }) else { return f64::NAN };
    let (val, _) = dssim.compare(img1, img2);
    val.into()
}