webp-container-spec: align anim pseudocode w/prose

- add missing 'or application-defined color' when creating the canvas
- reference 'dispose_method' before rendering image

Bug: webp:646
Change-Id: I25734d1912644f0aa6c87e14b80ed8cd9b180056
This commit is contained in:
James Zern 2024-07-16 15:38:13 -07:00
parent 6296cc8d0d
commit c9dd9bd40b

View File

@ -781,7 +781,8 @@ _VP8X.field_ means the field in the 'VP8X' Chunk with the same description.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
VP8X.flags.hasAnimation MUST be TRUE
canvas ← new image of size VP8X.canvasWidth x VP8X.canvasHeight with
background color ANIM.background_color.
background color ANIM.background_color or
application-defined color.
loop_count ← ANIM.loopCount
dispose_method ← Dispose to background color
if loop_count == 0:
@ -809,6 +810,7 @@ for loop = 0..loop_count - 1
bitstream subchunks not found in 'Frame Data' earlier MUST
be TRUE
frame_params.bitstream = bitstream_data
apply dispose_method.
render frame with frame_params.alpha and frame_params.bitstream
on canvas with top-left corner at (frame_params.frameX,
frame_params.frameY), using Blending method