Perspective transform broken on some iOS devices

[calebbergman]

I've ran into an issue with using perspective transform on some iOS devices using Ionic and Capacitor (i.e. WKWebView) - thus far an iPhone 6 and a iPad Air 2. I've put together a Github project demonstrating the issue.

I've tested on iPhone 7 and iPhone 8 and it's worked fine. I upgraded the iPad Air 2's OS to iOS 12.4; the issue persists.

EDIT: I decided a much smaller image made my life easier as regards getting the tensor data

Desired

Undesired (iPad Air 2 iOS 12.4)

Original

[rmhrisk]

I don’t know we have a iPad 2 in our test equipment. Can you share the values returned in the good and negative cases?

[calebbergman]

Certainly. Please let me know if there's anything I'm missing or can add that would be helpful.

Good case

// input (source tensor)
data: Uint8Array(384256)
dtype: "uint8"
empty: Uint8Array(384256)
get: ƒ (i0,i1,i2)
id: 6
index: ƒ (i0,i1,i2, v)
name: "Tensor:6"
offset: 0
set: ƒ (i0,i1,i2, v)
shape: [316, 304, 4]
size: 384256
stride: [1216, 4, 1]

// rect
data: Float32Array(8) [102, 5, 301, 42, 254, 315, 55, 279]
P: 959.6585846065385
angleA: 1.5847472567080332
angleB: 1.5574556992303161
angleC: 1.579275389553046
angleD: 1.5617069616881911
area: 56145.530856629484
ax: 102
ay: 5
bx: 301
by: 42
cx: 254
cy: 315
distA: 278.0017985553331
distB: 277.01624501101014
distC: 202.41047403728888
distD: 202.23006700290637
distE: 345.2593228285081
distF: 341.5918617297549
dx: 55
dy: 279

maxHeight: 277
maxWidth: 214

// output (transformed tensor)
data: Uint8Array(237112)
dtype: "uint8"
empty: Uint8Array(237112)
get: ƒ (i0,i1,i2)
id: 10
index: ƒ (i0,i1,i2, v)
name: "Tensor:10"
offset: 0
set: ƒ (i0,i1,i2, v)
shape: [277, 214, 4]
size: 237112
stride: [856, 4, 1]

Output tensor data

Negative case

// input
data: Uint8Array [255, 255, 255, 255, 255, 255, 255, 255, 255, 255, …] (384256)
dtype: "uint8"
empty: Uint8Array [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, …] (384256)
get: function(i0,i1,i2)
id: 1
index: function(i0,i1,i2, v)
name: "Tensor:1"
offset: 0
set: function(i0,i1,i2, v)
shape: [316, 304, 4] (3)
size: 384256
stride: [1216, 4, 1] (3)

// rect
data: Float32Array (8) [102, 5, 301, 42, 254, 315, 55, 279]
P: 959.6585846065385
angleA: 1.5847472567080332
angleB: 1.5574556992303161
angleC: 1.579275389553046
angleD: 1.5617069616881911
ax: 102
ay: 5
bx: 301
by: 42
cx: 254
cy: 315
distA: 278.0017985553331
distB: 277.01624501101014
distC: 202.41047403728888
distD: 202.23006700290637
distE: 345.2593228285081
distF: 341.5918617297549
dx: 55
dy: 279

maxHeight: 277
maxWidth: 214

// output
data: Uint8Array [0, 0, 0, 255, 5, 5, 5, 255, 3, 3, …] (237112)
dtype: "uint8"
empty: Uint8Array [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, …] (237112)
get: function(i0,i1,i2)
id: 5
index: function(i0,i1,i2, v)
name: "Tensor:5"
offset: 0
set: function(i0,i1,i2, v)
shape: [277, 214, 4] (3)
size: 237112
stride: [856, 4, 1] (3)

Output tensor data