我正在寻找一种使用 C/C++ 中的 Skia 库在 EGLTexture 上绘制文本的方法。我计划在启动期间在 SurfaceFlinger 出现之前在 Android 平台上运行一个程序。
请不要将我指向 Android Java 示例，因为这不是我想要的。我正在对帧缓冲区级别的 UI 问题进行故障排除。我正在寻找一种使用 Android 本机库（Skia 等）在 C/C++ 中执行此操作的方法。
我有一个示例程序，可以使用 SkBitmap 将图像渲染到 EGLTexture 上。我能够在监视器上显示它。我遵循相同的示例并提出了这样的策略。但它不起作用。
0) 用绿色清除屏幕
1) 创建大小为 640x480 的 SkBitmap。
2) 创建由 SkBitmap.lockPixels() 返回的像素缓冲区支持的 EGLTexture
3) 使用 SkCanvas 在 SkBitmap 上绘制文本。将位图上传到上面的纹理中。4）然后在当前表面上绘制纹理
我使用启动动画程序（android）作为我的起点。当我运行这个程序时，我看到的只是绿色。我检查了 EGL 调用的错误。他们似乎都成功了。谢谢你的帮助
在谷歌群组上发布了这个问题。来自谷歌的布赖恩在这里有一些建议： https ://groups.google.com/d/topic/skia-discuss/aC5f6HB4gSU/discussion
下面是实现上述内容的代码。
#define EXPECT_NO_GL_ERROR(stmt) \
do { \
stmt; \
const EGLint error_code = eglGetError(); \
if (EGL_SUCCESS != error_code){ \
LOGD("GLTest: GL error code %d at %s:%d", error_code, __FILE__, __LINE__); \
__android_log_assert("GLTest", "GLtest", "GlTest"); \
}\
} while(0)
struct Texture
{
GLint w;
GLint h;
GLuint id;
};
bool GLTest::frametest()
{
Texture texFrame;
// Paint screen with green color
glShadeModel (GL_FLAT);
glDisable (GL_DITHER);
glDisable (GL_SCISSOR_TEST);
glClearColor(0, 1, 0, 1);
glClear (GL_COLOR_BUFFER_BIT);
eglSwapBuffers(mDisplay, mSurface);
SkGraphics::Init();
SkBitmap bitmap;
bitmap.setConfig(SkBitmap::kARGB_8888_Config, 640, 480);
bitmap.allocPixels();
if (NO_ERROR != initTexture(&texFrame, bitmap))
{
LOGD("GLTest: Unable to create a texture that is backed by SkBitmap");
return false;
}
SkCanvas canvas(bitmap);
SkPaint textAttribs;
textAttribs.setColor(0xFFFFFFFF);
textAttribs.setTextSize(SkIntToScalar(24));
const nsecs_t startTime = systemTime();
int frame_count = 0;
do
{
nsecs_t now = systemTime();
double time = now - startTime;
canvas.drawColor(0xFF0000FF);
canvas.drawText("Hello world", strlen("Hello world"), 200, 400,
textAttribs);
initTexture(&texFrame, bitmap); // Upload bitmap into canvas
glEnable (GL_BLEND);
EXPECT_NO_GL_ERROR(glBindTexture(GL_TEXTURE_2D, texFrame.id));
EXPECT_NO_GL_ERROR(glDrawTexiOES(0, 0, 0, texFrame.w, texFrame.h));
EGLBoolean res = eglSwapBuffers(mDisplay, mSurface);
if (res == EGL_FALSE)
break;
frame_count++;
if (0 == (frame_count % 150))
LOGD("GLTest: Completed %d frames", frame_count);
// 12fps: don't animate too fast to preserve CPU
const nsecs_t sleepTime = 83333 - ns2us(systemTime() - now);
if (sleepTime > 0)
usleep(sleepTime);
} while (!exitPending());
return false;
}
status_t GLTest::initTexture(Texture* texture, SkBitmap &bitmap)
{
bitmap.lockPixels();
const int w = bitmap.width();
const int h = bitmap.height();
const void* p = bitmap.getPixels();
GLint crop[4] =
{ 0, h, w, -h };
texture->w = w;
texture->h = h;
EXPECT_NO_GL_ERROR(glGenTextures(1, &(texture->id)));
EXPECT_NO_GL_ERROR(glBindTexture(GL_TEXTURE_2D, texture->id));
switch (bitmap.getConfig())
{
case SkBitmap::kA8_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, w, h, 0, GL_ALPHA, GL_UNSIGNED_BYTE, p));
break;
case SkBitmap::kARGB_4444_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_SHORT_4_4_4_4, p));
break;
case SkBitmap::kARGB_8888_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, p));
break;
case SkBitmap::kRGB_565_Config:
EXPECT_NO_GL_ERROR(
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, p));
break;
default:
break;
}
EXPECT_NO_GL_ERROR(
glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_CROP_RECT_OES, crop));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT));
EXPECT_NO_GL_ERROR(
glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT));
return NO_ERROR;
}