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Special treatment for 1-class segmentation category mask output on GPU.

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PiperOrigin-RevId: 523271622
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MediaPipe Team 2023-04-10 19:11:08 -07:00 committed by Copybara-Service
parent 87ec846ed6
commit 3bb411e99d
2 changed files with 95 additions and 52 deletions
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52
mediapipe/tasks/cc/vision/image_segmenter/calculators/segmentation_postprocessor_gl.cc
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@ -185,6 +185,28 @@ void main() {
}
})";
// Special argmax shader for N=1 classes. We don't need to worry about softmax
// activation (it is assumed softmax requires N > 1 classes), but this should
// occur after SIGMOID activation if specified. Instead of a true argmax, we
// simply use 0.5 as the cutoff, assigning 1 (foreground) or 0 (background)
// based on whether the confidence value reaches this cutoff or not,
// respectively.
static constexpr char kArgmaxOneClassShader[] = R"(
DEFAULT_PRECISION(mediump, float)
in vec2 sample_coordinate;
uniform sampler2D input_texture;
void main() {
float input_val = texture2D(input_texture, sample_coordinate).x;
// Category is just value rounded to nearest integer; then we map to either
// 0 or 1/255 accordingly. If the input has been activated properly, then the
// values should always be in the range [0, 1]. But just in case it hasn't, to
// avoid category overflow issues when the activation function is not properly
// chosen, we add an extra clamp here, as performance hit is minimal.
float category = clamp(floor(input_val + 0.5), 0.0, 1.0);
gl_FragColor = vec4(category / 255.0, 0.0, 0.0, 1.0);
})";
// Softmax is in 3 steps:
// - First we find max over all masks
// - Then we transform all masks to be exp(val - maxval), and also add to
@ -377,11 +399,14 @@ absl::Status SegmentationPostprocessorGl::GlInit() {
"softmax normalization", kNormalizationShader,
{"sum_texture", "current_chunk"}, &softmax_normalization_shader_));
// Category mask shaders (Argmax)
// Category mask shaders (Argmax and special 1-class fg/bg argmax)
MP_RETURN_IF_ERROR(CreateBasicFragmentShaderProgram(
"argmax", kArgmaxShader,
{"prev_max_texture", "current_chunk", "num_channels", "argmax_offset"},
&argmax_shader_));
MP_RETURN_IF_ERROR(CreateBasicFragmentShaderProgram(
"one-class argmax", kArgmaxOneClassShader, {"input_texture"},
&argmax_one_class_shader_));
// Split shader. This is created separately since it uses a custom vertex
// shader. TODO: Refactor so this shares common init code as well.
@ -646,10 +671,25 @@ SegmentationPostprocessorGl::GetSegmentationResultGpu(const Shape& input_shape,
std::vector<GlTexture> outputs;
if (is_category_mask) {
// Step 3: For CATEGORY, apply argmax shader iteratively with each chunk
// to get a 2-channel texture representing "combined maxval" and "argmax",
// and then slice off the second channel for the category mask output,
// using our usual channel_select program.
// Step 3, N = 1: For CATEGORY with 1 class, use special FG/BG argmax
// shader instead of our usual N-class system.
if (num_outputs == 1) {
outputs.push_back(helper_.CreateDestinationTexture(
output_width, output_height, final_output_format));
helper_.BindFramebuffer(outputs.back());
glUseProgram(argmax_one_class_shader_.program);
glUniform1i(argmax_one_class_shader_.uniforms["input_texture"], 1);
glActiveTexture(GL_TEXTURE1);
// Only one chunk, and softmax cannot be applied to 1-class models
// anyways.
glBindTexture(GL_TEXTURE_2D, chunks[0].name());
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
} else {
// Step 3, N > 1: For CATEGORY with N classes, apply argmax shader
// iteratively with each chunk to get a 2-channel texture representing
// "combined maxval" and "argmax", and then slice off the second channel
// for the category mask output, using our usual channel_select program.
glUseProgram(argmax_shader_.program);
glUniform1i(argmax_shader_.uniforms["current_chunk"], 1);
glUniform1i(argmax_shader_.uniforms["prev_max_texture"], 2);
@ -702,6 +742,7 @@ SegmentationPostprocessorGl::GetSegmentationResultGpu(const Shape& input_shape,
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}
} else {
// Step 3: For CONFIDENCE, apply channel-select repeatedly to extract
// final textures.
@ -760,6 +801,7 @@ SegmentationPostprocessorGl::~SegmentationPostprocessorGl() {
glDeleteProgram(activation_shader_.program);
glDeleteProgram(argmax_shader_.program);
glDeleteProgram(argmax_one_class_shader_.program);
glDeleteProgram(channel_select_shader_.program);
glDeleteProgram(softmax_max_shader_.program);
glDeleteProgram(softmax_transform_and_sum_shader_.program);

1
mediapipe/tasks/cc/vision/image_segmenter/calculators/segmentation_postprocessor_gl.h
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@ -63,6 +63,7 @@ class SegmentationPostprocessorGl {
GlShader activation_shader_;
GlShader argmax_shader_;
GlShader argmax_one_class_shader_;
GlShader channel_select_shader_;
GlShader softmax_max_shader_;
GlShader softmax_transform_and_sum_shader_;