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webp-container-spec: change assert to MUST be TRUE

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in the 'Canvas Assembly from Frames' section. This matches the format in
the RFC draft; assert was not defined

Change-Id: Ib943b42f75fd1b4c281848f14e0626df9c868f59
This commit is contained in:
James Zern 2023-10-06 11:33:23 -07:00
parent cdbf88aed2
commit 9db21143d0
1 changed files with 8 additions and 6 deletions
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14
doc/webp-container-spec.txt
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@ -776,7 +776,7 @@ The following pseudocode illustrates the rendering process. The notation
_VP8X.field_ means the field in the 'VP8X' Chunk with the same description.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
assert VP8X.flags.hasAnimation
VP8X.flags.hasAnimation MUST be TRUE
canvas ← new image of size VP8X.canvasWidth x VP8X.canvasHeight with
background color ANIM.background_color.
loop_count ← ANIM.loopCount
@ -784,7 +784,7 @@ dispose_method ← Dispose to background color
if loop_count == 0:
loop_count = ∞
frame_params ← nil
assert next chunk in image_data is ANMF
next chunk in image_data is ANMF MUST be TRUE
for loop = 0..loop_count - 1
clear canvas to ANIM.background_color or application-defined color
until eof or non-ANMF chunk
@ -795,14 +795,16 @@ for loop = 0..loop_count - 1
frame_params.frameDuration = Frame Duration
frame_right = frame_params.frameX + frame_params.frameWidth
frame_bottom = frame_params.frameY + frame_params.frameHeight
assert VP8X.canvasWidth >= frame_right
assert VP8X.canvasHeight >= frame_bottom
VP8X.canvasWidth >= frame_right MUST be TRUE
VP8X.canvasHeight >= frame_bottom MUST be TRUE
for subchunk in 'Frame Data':
if subchunk.tag == "ALPH":
assert alpha subchunks not found in 'Frame Data' earlier
alpha subchunks not found in 'Frame Data' earlier MUST be
TRUE
frame_params.alpha = alpha_data
else if subchunk.tag == "VP8 " OR subchunk.tag == "VP8L":
assert bitstream subchunks not found in 'Frame Data' earlier
bitstream subchunks not found in 'Frame Data' earlier MUST
be TRUE
frame_params.bitstream = bitstream_data
render frame with frame_params.alpha and frame_params.bitstream
on canvas with top-left corner at (frame_params.frameX,