Fixed incorrect behaviour of headless_renderer depending on image dim…

…ensions (bevyengine#13388)

# Objective

- Fixes bevyengine#13384 .

## Solution

- If the image became wider when copying from the texture to the buffer,
then the data is reduced to its original size when copying from the
buffer to the image.

## Testing

- Ran example with 1919x1080 resolution

![000](https://github.com/bevyengine/bevy/assets/17225606/47d95ed7-1c8c-4be4-a45a-1f485a3d6aa7)

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: François Mockers <francois.mockers@vleue.com>

examples/app/headless_renderer.rs

@@ -13,16 +13,15 @@ use bevy::{
  prelude::*,
  render::{
  camera::RenderTarget,
- render_asset::RenderAssetUsages,
- render_asset::RenderAssets,
+ render_asset::{RenderAssetUsages, RenderAssets},
  render_graph::{self, NodeRunError, RenderGraph, RenderGraphContext, RenderLabel},
  render_resource::{
  Buffer, BufferDescriptor, BufferUsages, CommandEncoderDescriptor, Extent3d,
  ImageCopyBuffer, ImageDataLayout, Maintain, MapMode, TextureDimension, TextureFormat,
  TextureUsages,
  },
  renderer::{RenderContext, RenderDevice, RenderQueue},
- texture::BevyDefault,
+ texture::{BevyDefault, TextureFormatPixelInfo},
  Extract, Render, RenderApp, RenderSet,
  },
 };
@@ -361,6 +360,10 @@ impl render_graph::Node for ImageCopyDriver {
  let block_dimensions = src_image.texture_format.block_dimensions();
  let block_size = src_image.texture_format.block_copy_size(None).unwrap();
 
+ // Calculating correct size of image row because
+ // copy_texture_to_buffer can copy image only by rows aligned wgpu::COPY_BYTES_PER_ROW_ALIGNMENT
+ // That's why image in buffer can be little bit wider
+ // This should be taken into account at copy from buffer stage
  let padded_bytes_per_row = RenderDevice::align_copy_bytes_per_row(
  (src_image.size.x as usize / block_dimensions.0 as usize) * block_size as usize,
  );
@@ -492,7 +495,24 @@ fn update(
  for image in images_to_save.iter() {
  // Fill correct data from channel to image
  let img_bytes = images.get_mut(image.id()).unwrap();
- img_bytes.data.clone_from(&image_data);
+
+ // We need to ensure that this works regardless of the image dimensions
+ // If the image became wider when copying from the texture to the buffer,
+ // then the data is reduced to its original size when copying from the buffer to the image.
+ let row_bytes = img_bytes.width() as usize
+ * img_bytes.texture_descriptor.format.pixel_size();
+ let aligned_row_bytes = RenderDevice::align_copy_bytes_per_row(row_bytes);
+ if row_bytes == aligned_row_bytes {
+ img_bytes.data.clone_from(&image_data);
+ } else {
+ // shrink data to original image size
+ img_bytes.data = image_data
+ .chunks(aligned_row_bytes)
+ .take(img_bytes.height() as usize)
+ .flat_map(|row| &row[..row_bytes.min(row.len())])
+ .cloned()
+ .collect();
+ }
 
  // Create RGBA Image Buffer
  let img = match img_bytes.clone().try_into_dynamic() {