Perform degamma and gamma conversions on user request

benches/basic.rs

@@ -1,5 +1,5 @@
 use criterion::{criterion_group, criterion_main, Criterion};
-use ispc_downsampler::{downsample, Format, Image};
+use ispc_downsampler::{downsample, Format, Image, Parameters};
 use resize::{px::RGB, Type::Lanczos3};
 use stb_image::image::{load, LoadResult};
 use std::path::Path;
@@ -17,8 +17,15 @@ pub fn ispc_downsampler(c: &mut Criterion) {
         let target_width = (img.width / 4) as u32;
         let target_height = (img.height / 4) as u32;
 
+        let params = Parameters {
+            // Input stb Image is gamma-corrected (i.e. expects to be passed through a CRT with exponent 2.2)
+            degamma: true,
+            // Output image is PNG which must be stored with a gamma of 1/2.2
+            gamma: true,
+        };
+
         c.bench_function("Downsample `square_test.png` using ispc_downsampler", |b| {
-            b.iter(|| downsample(&src_img, target_width, target_height))
+            b.iter(|| downsample(&params, &src_img, target_width, target_height))
         });
     }
 }

examples/test.rs

@@ -1,5 +1,5 @@
 use image::{RgbImage, RgbaImage};
-use ispc_downsampler::{downsample, Format, Image};
+use ispc_downsampler::{downsample, Format, Image, Parameters};
 use stb_image::image::{load, LoadResult};
 use std::path::Path;
 use std::time::Instant;
@@ -26,7 +26,13 @@ fn main() {
 
             let now = Instant::now();
             println!("Downsampling started!");
-            let downsampled_pixels = downsample(&src_img, target_width, target_height);
+            let params = Parameters {
+                // Input stb Image is gamma-corrected (i.e. expects to be passed through a CRT with exponent 2.2)
+                degamma: false,
+                // Output image is PNG which must be stored with a gamma of 1/2.2
+                gamma: true,
+            };
+            let downsampled_pixels = downsample(&params, &src_img, target_width, target_height);
             println!("Finished downsampling in {:.2?}!", now.elapsed());
 
             std::fs::create_dir_all("example_outputs").unwrap();

src/ispc/downsample_ispc.rs

@@ -2,16 +2,171 @@
 pub mod downsample_ispc {
 /* automatically generated by rust-bindgen 0.61.0 */
 
+#[repr(C)]
+#[repr(align(16))]
+#[derive(Debug, Copy, Clone)]
+pub struct uint32_t2 {
+    pub v: [u32; 2usize],
+}
+#[test]
+fn bindgen_test_layout_uint32_t2() {
+    const UNINIT: ::std::mem::MaybeUninit<uint32_t2> = ::std::mem::MaybeUninit::uninit();
+    let ptr = UNINIT.as_ptr();
+    assert_eq!(
+        ::std::mem::size_of::<uint32_t2>(),
+        16usize,
+        concat!("Size of: ", stringify!(uint32_t2))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<uint32_t2>(),
+        16usize,
+        concat!("Alignment of ", stringify!(uint32_t2))
+    );
+    assert_eq!(
+        unsafe { ::std::ptr::addr_of!((*ptr).v) as usize - ptr as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(uint32_t2),
+            "::",
+            stringify!(v)
+        )
+    );
+}
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct Parameters {
+    pub degamma: bool,
+    pub gamma: bool,
+}
+#[test]
+fn bindgen_test_layout_Parameters() {
+    const UNINIT: ::std::mem::MaybeUninit<Parameters> = ::std::mem::MaybeUninit::uninit();
+    let ptr = UNINIT.as_ptr();
+    assert_eq!(
+        ::std::mem::size_of::<Parameters>(),
+        2usize,
+        concat!("Size of: ", stringify!(Parameters))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<Parameters>(),
+        1usize,
+        concat!("Alignment of ", stringify!(Parameters))
+    );
+    assert_eq!(
+        unsafe { ::std::ptr::addr_of!((*ptr).degamma) as usize - ptr as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(Parameters),
+            "::",
+            stringify!(degamma)
+        )
+    );
+    assert_eq!(
+        unsafe { ::std::ptr::addr_of!((*ptr).gamma) as usize - ptr as usize },
+        1usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(Parameters),
+            "::",
+            stringify!(gamma)
+        )
+    );
+}
+#[repr(C)]
+#[repr(align(16))]
+#[derive(Debug, Copy, Clone)]
+pub struct Image {
+    pub data: *mut u8,
+    pub __bindgen_padding_0: u64,
+    pub size: uint32_t2,
+}
+#[test]
+fn bindgen_test_layout_Image() {
+    const UNINIT: ::std::mem::MaybeUninit<Image> = ::std::mem::MaybeUninit::uninit();
+    let ptr = UNINIT.as_ptr();
+    assert_eq!(
+        ::std::mem::size_of::<Image>(),
+        32usize,
+        concat!("Size of: ", stringify!(Image))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<Image>(),
+        16usize,
+        concat!("Alignment of ", stringify!(Image))
+    );
+    assert_eq!(
+        unsafe { ::std::ptr::addr_of!((*ptr).data) as usize - ptr as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(Image),
+            "::",
+            stringify!(data)
+        )
+    );
+    assert_eq!(
+        unsafe { ::std::ptr::addr_of!((*ptr).size) as usize - ptr as usize },
+        16usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(Image),
+            "::",
+            stringify!(size)
+        )
+    );
+}
+#[repr(C)]
+#[repr(align(16))]
+#[derive(Debug, Copy, Clone)]
+pub struct FloatImage {
+    pub data: *mut f32,
+    pub __bindgen_padding_0: u64,
+    pub size: uint32_t2,
+}
+#[test]
+fn bindgen_test_layout_FloatImage() {
+    const UNINIT: ::std::mem::MaybeUninit<FloatImage> = ::std::mem::MaybeUninit::uninit();
+    let ptr = UNINIT.as_ptr();
+    assert_eq!(
+        ::std::mem::size_of::<FloatImage>(),
+        32usize,
+        concat!("Size of: ", stringify!(FloatImage))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<FloatImage>(),
+        16usize,
+        concat!("Alignment of ", stringify!(FloatImage))
+    );
+    assert_eq!(
+        unsafe { ::std::ptr::addr_of!((*ptr).data) as usize - ptr as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(FloatImage),
+            "::",
+            stringify!(data)
+        )
+    );
+    assert_eq!(
+        unsafe { ::std::ptr::addr_of!((*ptr).size) as usize - ptr as usize },
+        16usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(FloatImage),
+            "::",
+            stringify!(size)
+        )
+    );
+}
 extern "C" {
     pub fn resample(
-        width: u32,
-        height: u32,
-        stride: u32,
+        params: *const Parameters,
+        src: *const Image,
+        degamma: *mut FloatImage,
+        dst: *mut Image,
         num_channels: u8,
-        target_width: u32,
-        target_height: u32,
-        src_data: *const u8,
-        out_data: *mut u8,
     );
 }
 extern "C" {

src/ispc/kernels/image.ispc

@@ -1,4 +1,9 @@
 struct Image {
     uniform uint8* data;
-    uniform int<2> size;
+    uniform uint<2> size;
+};
+
+struct FloatImage {
+    uniform float* data;
+    uniform uint<2> size;
 };