I have a simple shader code. I pass in two image texture (NOTE: One is samplerExternalOES and other one is sampler2D).

The first texture 'sTexture' is the original image i get from a camera frame. The second texture 'sTexture2' is a mask i get from the cpu.

The shader fails on the 'mix' function.

The shader is as follows:

Code :
uniform samplerExternalOES sTexture;
uniform sampler2D sTexture2;
varying vec2 v_TexCoord;
void main(void)
    vec4 originalrgb = vec4((texture2D(sTexture, v_TexCoord).rgb), 1.0);
    vec4 floodfillimage = vec4((texture2D(sTexture2, v_TexCoord).rgb), 1.0);
    /*Code To Colour Input Image with Blue Tint Color*/
    vec4 c = vec4(0.0, 1.0, 1.0, 1); 
    vec4 inputColor = vec4((texture2D(sTexture, v_TexCoord).rgb), 1.0);
    float average = (inputColor.r + inputColor.g + inputColor.b) / 3.0;
    vec4 grayscale = vec4(average, average, average, 1.0);
    vec4 colorizedOutput = grayscale * c ;
    /*Code To mix original image with blue coloured based on another floodfilledimage passed in */
    gl_FragColor = mix(originalrgb.rgba, colorizedOutput.rgba, floodfillimage.r);

The error i recieve is glerror 1282, which means GL_INVALID_OPERATION. I've debugged and found out this happens on the mix function line.

NOTE: If I change the last line to
Code :
gl_FragColor = mix(originalrgb.rgba, colorizedOutput.rgba, 0.5);
, it works.

So, why is it that the code panics when i do
Code :

Thank You.

EDIT I've tested both textures passed in (ie, i just rendered them to gl_FragColor) and they both are the image they're suppose to be