axmol/core/renderer/shaders/label_outline.frag

/****************************************************************************
 Copyright (c) 2018-2019 Xiamen Yaji Software Co., Ltd.

 https://axmolengine.github.io/

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 of this software and associated documentation files (the "Software"), to deal
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 THE SOFTWARE.
 ****************************************************************************/
 
/*
 * LICENSE ???
 */
const char* labelOutline_frag = R"(
#ifdef GL_ES
precision lowp float;
#endif

varying vec4 v_fragmentColor;
varying vec2 v_texCoord;

uniform vec4 u_effectColor;
uniform vec4 u_textColor;
uniform sampler2D u_tex0;

#ifdef GL_ES
uniform lowp int u_effectType; // 0: None (Draw text), 1: Outline, 2: Shadow
#else
uniform int u_effectType;
#endif

void main()
{
    vec4 sample = texture2D(u_tex0, v_texCoord);
    // fontAlpha == 1 means the area of solid text (without edge)
    // fontAlpha == 0 means the area outside text, including outline area
    // fontAlpha == (0, 1) means the edge of text
    float fontAlpha = sample.a;

    // outlineAlpha == 1 means the area of 'solid text' and 'solid outline'
    // outlineAlpha == 0 means the transparent area outside text and outline
    // outlineAlpha == (0, 1) means the edge of outline
    float outlineAlpha = sample.r;

    if (u_effectType == 0) // draw text
    {
        gl_FragColor = v_fragmentColor * vec4(u_textColor.rgb, u_textColor.a * fontAlpha);
    }
    else if (u_effectType == 1) // draw outline
    {
        // multipy (1.0 - fontAlpha) to make the inner edge of outline smoother and make the text itself transparent.
        gl_FragColor = v_fragmentColor * vec4(u_effectColor.rgb, u_effectColor.a * outlineAlpha * (1.0 - fontAlpha));
    }
    else // draw shadow
    {
        gl_FragColor = v_fragmentColor * vec4(u_effectColor.rgb, u_effectColor.a * outlineAlpha);
    }
}
)";