Olive: Swirl effect removes transparency

[hellocatfood]

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System Information

Olive version: 675ea94
Source: PPA
Operating system: Ubuntu 18.10 64-bit
CPU: Intel i7
RAM: 8GB
GPU: NVIDIA Geforce GT 1030 2GB

Detailed Description

Adding a swirl effect to an transparent image removes transparency of the image. See gif below

Steps to reproduce

Add a video/image.
Overlay a transparent png
Add a swirl effect to the transparent image
Adjust the settings

[alcomposer]

This is already fixed in the FurtherOCIO branch. The shader also needs to work on the alpha:

#version 110

// Swirl effect parameters
uniform float radius;
uniform float angle;
uniform float center_x;
uniform float center_y;
uniform vec2 resolution;

uniform sampler2D myTexture;
varying vec2 vTexCoord;

void main(void) {
    vec2 center = vec2((resolution.x*0.5)+center_x, (resolution.y*0.5)+center_y);

    vec2 uv = vTexCoord.st;

    vec2 tc = uv * resolution;
    tc -= center;
    float dist = length(tc);
    if (dist < radius) {
        float percent = (radius - dist) / radius;
        float theta = percent * percent * (-angle*0.05) * 8.0;
        float s = sin(theta);
        float c = cos(theta);
        tc = vec2(dot(tc, vec2(c, -s)), dot(tc, vec2(s, c)));
    }
    tc += center;
    vec4 color = texture2D(myTexture, tc / resolution).rgba;  //<-- working on alpha as well (don't need the .rgba but I am spelling it our here
    gl_FragColor = color;
}

Above GLSL code running in current master:

There does seem to be a glitch with the order of drawing when a user does:

__Checkerboard -> Crop -> Swirl__

Here is what happens when a user puts the above chain together and then adjusts the crop values:

Alpha drawing issue in current furtherocio*:

* Issue present in master branch when using modified swirl.frag as shown above.

[itsmattkc]

I legitimately just discovered this yesterday, I have no idea why it was written like that.