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66 lines
1.7 KiB
C++
66 lines
1.7 KiB
C++
//
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// Screenshot.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 27/02/2019.
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// Copyright © 2019 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include "OpenGL.hpp"
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#include <algorithm>
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#include <vector>
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namespace Outputs::Display::OpenGL {
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/*!
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Upon construction, Screenshot will capture the centre portion of the currently-bound framebuffer,
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cropping to an image that matches the requested aspect ratio.
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The image will then be available as RGBA data, in raster order via the struct members.
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*/
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struct Screenshot {
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Screenshot(const int aspect_width, const int aspect_height) {
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// Get the current viewport to establish framebuffer size. Then determine how wide the
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// centre portion of that would be, allowing for the requested aspect ratio.
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GLint dimensions[4];
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glGetIntegerv(GL_VIEWPORT, dimensions);
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height = int(dimensions[3]);
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width = (height * aspect_width) / aspect_height;
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pixel_data.resize(size_t(width * height * 4));
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// Grab the framebuffer contents, temporarily setting single-byte alignment.
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int prior_alignment;
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glGetIntegerv(GL_PACK_ALIGNMENT, &prior_alignment);
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glReadPixels(
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(dimensions[2] - GLint(width)) >> 1,
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0,
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GLint(width),
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GLint(height),
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GL_RGBA,
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GL_UNSIGNED_BYTE,
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pixel_data.data()
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);
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glPixelStorei(GL_PACK_ALIGNMENT, prior_alignment);
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// Flip the contents into raster order.
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const size_t line_size = size_t(width * 4);
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for(size_t y = 0; y < size_t(height) / 2; ++y) {
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const size_t flipped_y = size_t(height - 1) - y;
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std::swap_ranges(
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&pixel_data[flipped_y * line_size],
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&pixel_data[flipped_y * line_size + line_size],
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&pixel_data[y * line_size]
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);
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}
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}
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std::vector<uint8_t> pixel_data;
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int width, height;
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};
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}
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