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b7b51d01c3
Creating a completely empty bitmap fails. Just write a 1x1 bitmap if the bitmap ends up empty for now.
102 lines
3.8 KiB
C++
102 lines
3.8 KiB
C++
/*
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* Copyright (c) 2024, Nico Weber <thakis@chromium.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibGfx/Bitmap.h>
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#include <LibGfx/ImageFormats/AnimationWriter.h>
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#include <LibGfx/Rect.h>
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namespace Gfx {
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AnimationWriter::~AnimationWriter() = default;
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static bool are_scanlines_equal(Bitmap const& a, Bitmap const& b, int y)
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{
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for (int x = 0; x < a.width(); ++x) {
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if (a.get_pixel(x, y) != b.get_pixel(x, y))
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return false;
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}
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return true;
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}
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static bool are_columns_equal(Bitmap const& a, Bitmap const& b, int x, int y1, int y2)
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{
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for (int y = y1; y < y2; ++y) {
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if (a.get_pixel(x, y) != b.get_pixel(x, y))
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return false;
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}
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return true;
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}
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static Gfx::IntRect rect_where_pixels_are_different(Bitmap const& a, Bitmap const& b)
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{
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VERIFY(a.size() == b.size());
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// FIXME: This works on physical pixels.
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VERIFY(a.scale() == 1);
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VERIFY(b.scale() == 1);
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int number_of_equal_pixels_at_top = 0;
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while (number_of_equal_pixels_at_top < a.height() && are_scanlines_equal(a, b, number_of_equal_pixels_at_top))
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++number_of_equal_pixels_at_top;
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int number_of_equal_pixels_at_bottom = 0;
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while (number_of_equal_pixels_at_bottom < a.height() - number_of_equal_pixels_at_top && are_scanlines_equal(a, b, a.height() - number_of_equal_pixels_at_bottom - 1))
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++number_of_equal_pixels_at_bottom;
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int const y1 = number_of_equal_pixels_at_top;
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int const y2 = a.height() - number_of_equal_pixels_at_bottom;
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int number_of_equal_pixels_at_left = 0;
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while (number_of_equal_pixels_at_left < a.width() && are_columns_equal(a, b, number_of_equal_pixels_at_left, y1, y2))
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++number_of_equal_pixels_at_left;
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int number_of_equal_pixels_at_right = 0;
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while (number_of_equal_pixels_at_right < a.width() - number_of_equal_pixels_at_left && are_columns_equal(a, b, a.width() - number_of_equal_pixels_at_right - 1, y1, y2))
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++number_of_equal_pixels_at_right;
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// WebP can only encode even-sized animation frame positions.
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// FIXME: Change API shape in some way so that the AnimationWriter base class doesn't have to know about this detail of a subclass.
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if (number_of_equal_pixels_at_left % 2 != 0)
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--number_of_equal_pixels_at_left;
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if (number_of_equal_pixels_at_top % 2 != 0)
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--number_of_equal_pixels_at_top;
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Gfx::IntRect rect;
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rect.set_x(number_of_equal_pixels_at_left);
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rect.set_y(number_of_equal_pixels_at_top);
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rect.set_width(a.width() - number_of_equal_pixels_at_left - number_of_equal_pixels_at_right);
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rect.set_height(a.height() - number_of_equal_pixels_at_top - number_of_equal_pixels_at_bottom);
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return rect;
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}
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ErrorOr<void> AnimationWriter::add_frame_relative_to_last_frame(Bitmap& frame, int duration_ms, RefPtr<Bitmap> last_frame)
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{
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if (!last_frame)
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return add_frame(frame, duration_ms);
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auto rect = rect_where_pixels_are_different(*last_frame, frame);
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if (rect.is_empty()) {
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// The frame is identical to the last frame. Don't store an empty bitmap.
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// FIXME: We could delay writing the last frame until we know that the next frame is different,
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// and just keep increasing that frame's duration instead.
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rect = { 0, 0, 1, 1 };
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}
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// FIXME: It would be nice to have a way to crop a bitmap without copying the data.
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auto differences = TRY(frame.cropped(rect));
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// FIXME: Another idea: If all frames of the animation have no alpha,
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// this could set color values of pixels that are in the changed rect that are
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// equal to the last frame to transparent black and set the frame to be blended.
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// That might take less space after compression.
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// This assumes a replacement disposal method.
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return add_frame(differences, duration_ms, rect.location());
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}
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}
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