glTexSubImage2D 在使用 FreeType 的 Android NDK 上的 OpenGL ES 3.2 中抛出 GL_INVALID_OPERATION

Question

我正在使用 NDK 将游戏从 PC 移植到 Android，并使用 FreeType 进行文本渲染。原始代码在使用 OpenGL 1.2 的 PC 上运行良好，为了在 Android 上运行，我决定将着色器程序更改为 OpenGL ES 3.2，但不幸的是，在第 glTexSubImage2D 行之后，我收到错误代码 1282 GL_INVALID_OPERATION，可能是什么原因为了这 ？ 着色器：

        const char *vertexShaderSource =
                "#version 320 es\n"
                "precision highp float;"
                "in vec4 coord;"
                "in vec4 color;"
                "out vec2 texpos;"
                "out vec4 colormod;"
                "uniform vec2 screensize;"
                "uniform int yoffset;"

                "void main(void)"
                "{"
                "   float x = ((coord.x - 400.0) / screensize.x) * (screensize.y / 300.0);"
                "   float y = ((300.0 - (coord.y + float(yoffset))) / screensize.y) * (screensize.y / 300.0);"
                "   gl_Position = vec4(x, y, 0.0, 1.0);"
                "   texpos = coord.zw;"
                "   colormod = color;"
                "}";

        const char *fragmentShaderSource =
                "#version 320 es\n"
                "precision highp float;"
                "in vec2 texpos;"
                "in vec4 colormod;"
                "out vec4 FragColor;"
                "uniform sampler2D texture;"
                "uniform vec2 atlassize;"
                "uniform int fontregion;"

                "void main(void)"
                "{"
                "   if (texpos.y == 0.0)"
                "   {"
                "       FragColor = colormod;"
                "   }"
                "   else if (texpos.y <= float(fontregion))"
                "   {"
                "       FragColor = vec4(1.0, 1.0, 1.0, texture(texture, texpos / atlassize).r) * colormod;"
                "   }"
                "   else"
                "   {"
                "       FragColor = texture(texture, texpos / atlassize).bgra * "
                "colormod;"
                "   }"
                "}";

    GLint attribute_coord_;
    GLint attribute_color_;
    GLint uniform_texture_;
    GLint uniform_atlas_size_;
    GLint uniform_screen_size_;
    GLint uniform_yoffset;
    GLint uniform_font_region_;

        attribute_coord_ = glGetAttribLocation(shader_program_, "coord");
        attribute_color_ = glGetAttribLocation(shader_program_, "color");
        uniform_texture_ = glGetUniformLocation(shader_program_, "texture");
        uniform_atlas_size_ = glGetUniformLocation(shader_program_, "atlassize");
        uniform_screen_size_ = glGetUniformLocation(shader_program_, "screensize");
        uniform_yoffset = glGetUniformLocation(shader_program_, "yoffset");
        uniform_font_region_ = glGetUniformLocation(shader_program_, "fontregion");

顶点缓冲区对象：

        glGenBuffers(1, &VBO_);

        glGenTextures(1, &atlas_);
        glBindTexture(GL_TEXTURE_2D, atlas_);
        glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTexImage2D(GL_TEXTURE_2D,
                     0,
                     GL_RGBA,
                     ATLASW,
                     ATLASH,
                     0,
                     GL_RGBA,
                     GL_UNSIGNED_BYTE,
                     nullptr);

        font_border.set_y(1);

从Android系统路径读取字体：/system/fonts/Roboto-Regular.ttf

const std::string FONT_NORMAL = Setting<FontPathNormal>().get().load();
const char *FONT_NORMAL_STR = FONT_NORMAL.c_str();
add_font(FONT_NORMAL_STR, Text::Font::A11M, 0, 11);

Freetype 加载字体：

    bool GraphicsGL::add_font(const char *name,
                              Text::Font id,
                              FT_UInt pixelw,
                              FT_UInt pixelh) {
        FT_Face face;

        if (FT_New_Face(ft_library_, name, 0, &face)) {
            std::cerr << "Error: Failed to create new face." << std::endl;
            return false;
        }

        if (FT_Set_Pixel_Sizes(face, pixelw, pixelh)) {
            std::cerr << "Error: Failed to set pixel sizes." << std::endl;
            return false;
        }

        FT_GlyphSlot g = face->glyph;

        GLshort width = 0;
        GLshort height = 0;

        for (uint32_t c = 32; c < 256; c++) {
            if (FT_Load_Char(face, c, FT_LOAD_RENDER)) {
                std::cerr << "Error: Failed to load a glyph into the glyph slot of "
                             "a face object."
                          << std::endl;
                continue;
            }

            auto w = static_cast<GLshort>(g->bitmap.width);
            auto h = static_cast<GLshort>(g->bitmap.rows);

            width += w;

            if (h > height) {
                height = h;
            }
        }

        if (font_border.x() + width > ATLASW) {
            font_border.set_x(0);
            font_border.set_y(font_ymax);
            font_ymax = 0;
        }

        GLshort x = font_border.x();
        GLshort y = font_border.y();

        font_border.shift_x(width);

        if (height > font_ymax) {
            font_ymax = height;
        }

        fonts_[id] = Font(width, height);

        GLshort ox = x;
        GLshort oy = y;

        for (uint32_t c = 32; c < 256; c++) {
            if (FT_Load_Char(face, c, FT_LOAD_RENDER)) {
                std::cerr << "Error: Failed to load a glyph into the glyph slot of "
                             "a face object."
                          << std::endl;
                continue;
            }

            auto ax = static_cast<GLshort>(g->advance.x >> 6);
            auto ay = static_cast<GLshort>(g->advance.y >> 6);
            auto l = static_cast<GLshort>(g->bitmap_left);
            auto t = static_cast<GLshort>(g->bitmap_top);
            auto w = static_cast<GLshort>(g->bitmap.width);
            auto h = static_cast<GLshort>(g->bitmap.rows);

            glTexSubImage2D(GL_TEXTURE_2D,
                            0,
                            ox,
                            oy,
                            w,
                            h,
                            GL_RED,
                            GL_UNSIGNED_BYTE,
                            g->bitmap.buffer);
            GLenum error = glGetError();

            Offset offset = Offset(ox, oy, w, h);
            fonts_[id].chars[c] = { ax, ay, w, h, l, t, offset };

            ox += w;
        }

        return true;
    }

Answer 1

根据 glTexSubImage2D 参考：

如果先前指定的纹理数组、格式和类型的internalFormat 的组合无效，则生成

GL_INVALID_OPERATION

。

在您的代码中，

glTexImage2D

调用指定

internalFormat

的

GL_RGBA

，根据glTexImage2D参考（表1）

GL_RGBA

内部格式仅支持多种类型的

GL_RGBA

格式（

GL_UNSIGNED_BYTE

、

GL_UNSIGNED_SHORT_4_4_4_4

、

GL_UNSIGNED_SHORT_5_5_5_1

）

您在

GL_RED

 中使用的 

glTexSubImage2D

不是受支持的格式之一，因此操作结果为

GL_INVALID_OPERATION

。

对于您的使用来说，

GL_RED

确实是

glTexSubImage2D

的有效格式，因为FreeType默认以8位灰度位图渲染，但您应该使用兼容的格式初始化纹理（内部格式

GL_R8

，格式

GL_RED

） ，输入

GL_UNSIGNED_BYTE

）并使用片段着色器提取 red 组件并生成可混合输出。