4 #include "padding_effect.h"
7 PaddingEffect::PaddingEffect()
8 : border_color(0.0f, 0.0f, 0.0f, 0.0f),
14 register_vec4("border_color", (float *)&border_color);
15 register_int("width", &output_width);
16 register_int("height", &output_height);
17 register_float("top", &top);
18 register_float("left", &left);
21 std::string PaddingEffect::output_fragment_shader()
23 return read_file("padding_effect.frag");
26 void PaddingEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
28 Effect::set_gl_state(glsl_program_num, prefix, sampler_num);
32 (output_height - input_height - top) / output_height
34 set_uniform_vec2(glsl_program_num, prefix, "offset", offset);
37 float(output_width) / input_width,
38 float(output_height) / input_height
40 set_uniform_vec2(glsl_program_num, prefix, "scale", scale);
42 // Due to roundoff errors, the test against 0.5 is seldom exact,
43 // even though we test for less than and not less-than-or-equal.
44 // We'd rather keep an extra border pixel in those very rare cases
45 // (where the image is shifted pretty much exactly a half-pixel)
46 // than losing a pixel in the common cases of integer shift.
47 // Thus the 1e-3 fudge factors.
48 float texcoord_min[2] = {
49 float((0.5f - 1e-3) / input_width),
50 float((0.5f - 1e-3) / input_height)
52 set_uniform_vec2(glsl_program_num, prefix, "texcoord_min", texcoord_min);
54 float texcoord_max[2] = {
55 float(1.0f - (0.5f - 1e-3) / input_width),
56 float(1.0f - (0.5f - 1e-3) / input_height)
58 set_uniform_vec2(glsl_program_num, prefix, "texcoord_max", texcoord_max);
61 // We don't change the pixels of the image itself, so the only thing that
62 // can make us less flexible is if the border color can be interpreted
63 // differently in different modes.
65 // 0.0 and 1.0 are interpreted the same, no matter the gamma ramp.
66 // Alpha is not affected by gamma.
67 bool PaddingEffect::needs_linear_light() const
69 if ((border_color.r == 0.0 || border_color.r == 1.0) &&
70 (border_color.g == 0.0 || border_color.g == 1.0) &&
71 (border_color.b == 0.0 || border_color.b == 1.0)) {
77 // The white point is the same (D65) in all the color spaces we currently support,
78 // so any gray would be okay, but we don't really have a guarantee for that.
79 // Stay safe and say that only pure black and pure white is okay.
80 // Alpha is not affected by color space.
81 bool PaddingEffect::needs_srgb_primaries() const
83 if (border_color.r == 0.0 && border_color.g == 0.0 && border_color.b == 0.0) {
86 if (border_color.r == 1.0 && border_color.g == 1.0 && border_color.b == 1.0) {
92 Effect::AlphaHandling PaddingEffect::alpha_handling() const
94 // If the border color is black, it doesn't matter if we're pre- or postmultiplied.
95 // Note that for non-solid black (i.e. alpha < 1.0), we're equally fine with
96 // pre- and postmultiplied, but later effects might change this status
97 // (consider e.g. blur), so setting DONT_CARE_ALPHA_TYPE is inappropriate,
98 // as it propagate blank alpha through this effect.
99 if (border_color.r == 0.0 && border_color.g == 0.0 && border_color.b == 0.0 && border_color.a == 1.0) {
100 return DONT_CARE_ALPHA_TYPE;
103 // If the border color is solid, we preserve blank alpha, as we never output any
104 // new non-solid pixels.
105 if (border_color.a == 1.0) {
106 return INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK;
109 // Otherwise, we're going to output our border color in premultiplied alpha,
110 // so the other pixels better be premultiplied as well.
111 return INPUT_AND_OUTPUT_PREMULTIPLIED_ALPHA;
114 void PaddingEffect::get_output_size(unsigned *width, unsigned *height, unsigned *virtual_width, unsigned *virtual_height) const
116 *virtual_width = *width = output_width;
117 *virtual_height = *height = output_height;
120 void PaddingEffect::inform_input_size(unsigned input_num, unsigned width, unsigned height)
122 assert(input_num == 0);
124 input_height = height;