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Introduce ImageData::get_rect

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We use that to send only the pixels that will be actually drawn to the
canvas thread in CanvasRenderingContext2d::PutImageData.

We also make the canvas thread byte swap and premultiply colours in-place.
This commit is contained in:
Anthony Ramine 2018-10-06 01:10:34 +02:00
parent 784fbb2bc1
commit 19f40cdf0b
5 changed files with 52 additions and 55 deletions
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45
components/canvas/canvas_data.rs
View file

@ -13,6 +13,7 @@ use cssparser::RGBA;
use euclid::{Transform2D, Point2D, Vector2D, Rect, Size2D};
use ipc_channel::ipc::{IpcBytesSender, IpcSender};
use num_traits::ToPrimitive;
use pixels;
use serde_bytes::ByteBuf;
use std::mem;
use std::sync::Arc;
@ -451,42 +452,22 @@ impl<'a> CanvasData<'a> {
// https://html.spec.whatwg.org/multipage/#dom-context-2d-putimagedata
pub fn put_image_data(
&mut self,
imagedata: Vec<u8>,
mut imagedata: Vec<u8>,
offset: Vector2D<i32>,
image_data_size: Size2D<i32>,
dest_rect: Rect<i32>,
imagedata_size: Size2D<i32>,
) {
assert_eq!(image_data_size.width * image_data_size.height * 4, imagedata.len() as i32);
let image_size = image_data_size;
let first_pixel = dest_rect.origin;
let mut src_line = (first_pixel.y * (image_size.width * 4) + first_pixel.x * 4) as usize;
let mut dest =
Vec::with_capacity((dest_rect.size.width * dest_rect.size.height * 4) as usize);
for _ in 0 .. dest_rect.size.height {
let mut src_offset = src_line;
for _ in 0 .. dest_rect.size.width {
let alpha = imagedata[src_offset + 3] as u16;
// add 127 before dividing for more accurate rounding
let premultiply_channel = |channel: u8| (((channel as u16 * alpha) + 127) / 255) as u8;
dest.push(premultiply_channel(imagedata[src_offset + 2]));
dest.push(premultiply_channel(imagedata[src_offset + 1]));
dest.push(premultiply_channel(imagedata[src_offset + 0]));
dest.push(imagedata[src_offset + 3]);
src_offset += 4;
}
src_line += (image_size.width * 4) as usize;
}
assert_eq!(imagedata_size.area() * 4, imagedata.len() as i32);
pixels::byte_swap_and_premultiply_inplace(&mut imagedata);
if let Some(source_surface) = self.drawtarget.create_source_surface_from_data(
&dest,
dest_rect.size,
dest_rect.size.width * 4,
&imagedata,
imagedata_size,
imagedata_size.width * 4,
SurfaceFormat::B8G8R8A8) {
self.drawtarget.copy_surface(source_surface, Rect::from_size(dest_rect.size), offset.to_point());
self.drawtarget.copy_surface(
source_surface,
Rect::from_size(imagedata_size),
offset.to_point(),
);
}
}