expose texture/image conversions as From/TryFrom (#2175)

fixes #2169 

Instead of having custom methods with reduced visibility, implement `From<image::DynamicImage> for Texture` and `TryFrom<Texture> for image::DynamicImage`

crates/bevy_render/src/texture/image_texture_conversion.rs

@@ -1,7 +1,10 @@
+use std::convert::TryFrom;
+use thiserror::Error;
+
 use super::{Extent3d, Texture, TextureDimension, TextureFormat};
 
-/// Helper method to convert a `DynamicImage` to a `Texture`
-pub(crate) fn image_to_texture(dyn_img: image::DynamicImage) -> Texture {
+impl From<image::DynamicImage> for Texture {
+    fn from(dyn_img: image::DynamicImage) -> Self {
         use bevy_core::cast_slice;
         let width;
         let height;
@@ -61,7 +64,6 @@ pub(crate) fn image_to_texture(dyn_img: image::DynamicImage) -> Texture {
                 width = i.width();
                 height = i.height();
                 format = TextureFormat::R16Uint;
-
                 let raw_data = i.into_raw();
 
                 data = cast_slice(&raw_data).to_owned();
@@ -89,7 +91,7 @@ pub(crate) fn image_to_texture(dyn_img: image::DynamicImage) -> Texture {
                     let r = pixel[0];
                     let g = pixel[1];
                     let b = pixel[2];
-                let a = u16::max_value();
+                    let a = u16::MAX;
 
                     local_data.extend_from_slice(&r.to_ne_bytes());
                     local_data.extend_from_slice(&g.to_ne_bytes());
@@ -116,36 +118,43 @@ pub(crate) fn image_to_texture(dyn_img: image::DynamicImage) -> Texture {
             data,
             format,
         )
-}
-
-/// Helper method to convert a `Texture` to a `DynamicImage`. Not all `Texture` formats are
-/// covered, it will return `None` if the format is not supported
-pub(crate) fn texture_to_image(texture: &Texture) -> Option<image::DynamicImage> {
-    match texture.format {
-        TextureFormat::R8Unorm => image::ImageBuffer::from_raw(
-            texture.size.width,
-            texture.size.height,
-            texture.data.clone(),
-        )
-        .map(image::DynamicImage::ImageLuma8),
-        TextureFormat::Rg8Unorm => image::ImageBuffer::from_raw(
-            texture.size.width,
-            texture.size.height,
-            texture.data.clone(),
-        )
-        .map(image::DynamicImage::ImageLumaA8),
-        TextureFormat::Rgba8UnormSrgb => image::ImageBuffer::from_raw(
-            texture.size.width,
-            texture.size.height,
-            texture.data.clone(),
-        )
-        .map(image::DynamicImage::ImageRgba8),
-        TextureFormat::Bgra8UnormSrgb => image::ImageBuffer::from_raw(
-            texture.size.width,
-            texture.size.height,
-            texture.data.clone(),
-        )
-        .map(image::DynamicImage::ImageBgra8),
-        _ => None,
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, Error, PartialEq)]
+pub enum TextureConversionError {
+    #[error("Unsupported texture format")]
+    UnsupportedFormat,
+    #[error("Invalid texture size")]
+    InvalidSize,
+}
+
+impl TryFrom<Texture> for image::DynamicImage {
+    type Error = TextureConversionError;
+
+    fn try_from(texture: Texture) -> Result<Self, Self::Error> {
+        match texture.format {
+            TextureFormat::R8Unorm => {
+                image::ImageBuffer::from_raw(texture.size.width, texture.size.height, texture.data)
+                    .map(image::DynamicImage::ImageLuma8)
+                    .ok_or(TextureConversionError::InvalidSize)
+            }
+            TextureFormat::Rg8Unorm => {
+                image::ImageBuffer::from_raw(texture.size.width, texture.size.height, texture.data)
+                    .map(image::DynamicImage::ImageLumaA8)
+                    .ok_or(TextureConversionError::InvalidSize)
+            }
+            TextureFormat::Rgba8UnormSrgb => {
+                image::ImageBuffer::from_raw(texture.size.width, texture.size.height, texture.data)
+                    .map(image::DynamicImage::ImageRgba8)
+                    .ok_or(TextureConversionError::InvalidSize)
+            }
+            TextureFormat::Bgra8UnormSrgb => {
+                image::ImageBuffer::from_raw(texture.size.width, texture.size.height, texture.data)
+                    .map(image::DynamicImage::ImageBgra8)
+                    .ok_or(TextureConversionError::InvalidSize)
+            }
+            _ => Err(TextureConversionError::UnsupportedFormat),
+        }
     }
 }

crates/bevy_render/src/texture/texture.rs

@@ -1,7 +1,6 @@
-use super::{
-    image_texture_conversion::image_to_texture, Extent3d, SamplerDescriptor, TextureDescriptor,
-    TextureDimension, TextureFormat,
-};
+use std::convert::TryInto;
+
+use super::{Extent3d, SamplerDescriptor, TextureDescriptor, TextureDimension, TextureFormat};
 use crate::renderer::{
     RenderResource, RenderResourceContext, RenderResourceId, RenderResourceType,
 };
@@ -135,9 +134,10 @@ impl Texture {
     /// - `TextureFormat::Rg8Unorm`
     /// - `TextureFormat::Rgba8UnormSrgb`
     /// - `TextureFormat::Bgra8UnormSrgb`
-    pub fn convert(&self, new_format: TextureFormat) -> Option<Self> {
-        super::image_texture_conversion::texture_to_image(self)
-            .and_then(|img| match new_format {
+    pub fn convert(self, new_format: TextureFormat) -> Option<Self> {
+        self.try_into()
+            .ok()
+            .and_then(|img: image::DynamicImage| match new_format {
                 TextureFormat::R8Unorm => Some(image::DynamicImage::ImageLuma8(img.into_luma8())),
                 TextureFormat::Rg8Unorm => {
                     Some(image::DynamicImage::ImageLumaA8(img.into_luma_alpha8()))
@@ -150,7 +150,7 @@ impl Texture {
                 }
                 _ => None,
             })
-            .map(super::image_texture_conversion::image_to_texture)
+            .map(|image| image.into())
     }
 
     pub fn texture_resource_system(
@@ -243,7 +243,7 @@ impl Texture {
         // cases.
 
         let dyn_img = image::load_from_memory_with_format(buffer, format)?;
-        Ok(image_to_texture(dyn_img))
+        Ok(dyn_img.into())
     }
 }
 

crates/bevy_sprite/src/texture_atlas_builder.rs

@@ -113,7 +113,7 @@ impl TextureAtlasBuilder {
     ) {
         if self.format == texture.format {
             Self::copy_texture_to_atlas(atlas_texture, texture, packed_location);
-        } else if let Some(converted_texture) = texture.convert(self.format) {
+        } else if let Some(converted_texture) = texture.clone().convert(self.format) {
             debug!(
                 "Converting texture from '{:?}' to '{:?}'",
                 texture.format, self.format