Add an effect for padding.

[movit] / padding_effect.cpp

diff --git a/padding_effect.cpp b/padding_effect.cpp
new file mode 100644 (file)
index 0000000..9d6e292
--- /dev/null
+++ b/padding_effect.cpp
@@ -0,0 +1,113 @@
+#include <math.h>
+#include <GL/glew.h>
+
+#include "padding_effect.h"
+#include "util.h"
+
+PaddingEffect::PaddingEffect()
+       : border_color(0.0f, 0.0f, 0.0f, 0.0f),
+         output_width(1280),
+         output_height(720),
+         top(0),
+         left(0)
+{
+       register_vec4("border_color", (float *)&border_color);
+       register_int("width", &output_width);
+       register_int("height", &output_height);
+       register_float("top", &top);
+       register_float("left", &left);
+}
+
+std::string PaddingEffect::output_fragment_shader()
+{
+       return read_file("padding_effect.frag");
+}
+
+void PaddingEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
+{
+       Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
+
+       float offset[2] = {
+               left / output_width,
+               (output_height - input_height - top) / output_height
+       };
+       set_uniform_vec2(glsl_program_num, prefix, "offset", offset);
+
+       float scale[2] = {
+               float(output_width) / input_width,
+               float(output_height) / input_height
+       };
+       set_uniform_vec2(glsl_program_num, prefix, "scale", scale);
+
+       // Due to roundoff errors, the test against 0.5 is seldom exact,
+       // even though we test for less than and not less-than-or-equal.
+       // We'd rather keep an extra border pixel in those very rare cases
+       // (where the image is shifted pretty much exactly a half-pixel)
+       // than losing a pixel in the common cases of integer shift.
+       // Thus the 1e-3 fudge factors.
+       float texcoord_min[2] = {
+               (0.5f - 1e-3) / input_width,
+               (0.5f - 1e-3) / input_height
+       };
+       set_uniform_vec2(glsl_program_num, prefix, "texcoord_min", texcoord_min);
+
+       float texcoord_max[2] = {
+               1.0f - (0.5f - 1e-3) / input_width,
+               1.0f - (0.5f - 1e-3) / input_height
+       };
+       set_uniform_vec2(glsl_program_num, prefix, "texcoord_max", texcoord_max);
+}
+       
+// We don't change the pixels of the image itself, so the only thing that 
+// can make us less flexible is if the border color can be interpreted
+// differently in different modes.
+
+// 0.0 and 1.0 are interpreted the same, no matter the gamma ramp.
+// Alpha is not affected by gamma.
+bool PaddingEffect::needs_linear_light() const
+{
+       if ((border_color.r == 0.0 || border_color.r == 1.0) &&
+           (border_color.g == 0.0 || border_color.g == 1.0) &&
+           (border_color.b == 0.0 || border_color.b == 1.0)) {
+               return false;
+       }
+       return true;
+}
+
+// The white point is the same (D65) in all the color spaces we currently support,
+// so any gray would be okay, but we don't really have a guarantee for that.
+// Stay safe and say that only pure black and pure white is okay.
+// Alpha is not affected by color space.
+bool PaddingEffect::needs_srgb_primaries() const
+{
+       if (border_color.r == 0.0 && border_color.g == 0.0 && border_color.b == 0.0) {
+               return false;
+       }
+       if (border_color.r == 1.0 && border_color.g == 1.0 && border_color.b == 1.0) {
+               return false;
+       }
+       return true;
+}
+
+// If the border color is black, it doesn't matter if we're pre- or postmultiplied
+// (or even blank, as a hack). Otherwise, it does.
+Effect::AlphaHandling PaddingEffect::alpha_handling() const
+{
+       if (border_color.r == 0.0 && border_color.g == 0.0 && border_color.b == 0.0) {
+               return DONT_CARE_ALPHA_TYPE;
+       }
+       return INPUT_AND_OUTPUT_ALPHA_PREMULTIPLIED;
+}
+       
+void PaddingEffect::get_output_size(unsigned *width, unsigned *height) const
+{
+       *width = output_width;
+       *height = output_height;
+}
+       
+void PaddingEffect::inform_input_size(unsigned input_num, unsigned width, unsigned height)
+{
+       assert(input_num == 0);
+       input_width = width;
+       input_height = height;
+}