From 6bb3a908d34728fec0a3520eac03ad9b69dd4a9b Mon Sep 17 00:00:00 2001 From: wolfbeast Date: Sat, 14 Jul 2018 05:11:39 +0200 Subject: Switch to Lanczos scaling from Hamming to get acceptable fast downscaling. In visual tests we see that Hamming-1 is not as good as Lanczos-2, however it is about 40% faster, and Lanczos-2 itself is about 30% faster than Lanczos-3. The use of Hamming-1 has been deemed an unacceptable trade-off between quality and speed due to the limited pixel space it operates in, so we pick Lanczos-2 here. On modern hardware, Lanczos-2 doesn't have any noticeable impact in normal use. --- gfx/2d/image_operations.cpp | 25 ++++++++++--------------- 1 file changed, 10 insertions(+), 15 deletions(-) (limited to 'gfx/2d') diff --git a/gfx/2d/image_operations.cpp b/gfx/2d/image_operations.cpp index 62215f007..79fa879d9 100644 --- a/gfx/2d/image_operations.cpp +++ b/gfx/2d/image_operations.cpp @@ -1,4 +1,5 @@ // Copyright (c) 2006-2012 The Chromium Authors. All rights reserved. +// Copyright (c) 2018 Mark Straver BASc. All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions @@ -107,7 +108,7 @@ void ComputeFilters(ImageOperations::ResizeMethod method, // Compute the unnormalized filter value at each location of the source // it covers. - float filter_sum = 0.0f; // Sub of the filter values for normalizing. + float filter_sum = 0.0f; // Sum of the filter values for normalizing. for (int cur_filter_pixel = src_begin; cur_filter_pixel <= src_end; cur_filter_pixel++) { // Distance from the center of the filter, this is the filter coordinate @@ -158,28 +159,22 @@ void ComputeFilters(ImageOperations::ResizeMethod method, ImageOperations::ResizeMethod ResizeMethodToAlgorithmMethod( ImageOperations::ResizeMethod method) { - // Convert any "Quality Method" into an "Algorithm Method" + // If we already have an "Algorithm Method", just return that. if (method >= ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD && method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD) { return method; } - // The call to ImageOperationsGtv::Resize() above took care of - // GPU-acceleration in the cases where it is possible. So now we just - // pick the appropriate software method for each resize quality. + // Convert any "Quality Method" into an "Algorithm Method" switch (method) { - // Users of RESIZE_GOOD are willing to trade a lot of quality to - // get speed, allowing the use of linear resampling to get hardware - // acceleration (SRB). Hence any of our "good" software filters - // will be acceptable, and we use the fastest one, Hamming-1. case ImageOperations::RESIZE_GOOD: - // Users of RESIZE_BETTER are willing to trade some quality in order - // to improve performance, but are guaranteed not to devolve to a linear - // resampling. In visual tests we see that Hamming-1 is not as good as - // Lanczos-2, however it is about 40% faster and Lanczos-2 itself is + // Users of RESIZE_GOOD are willing to trade quality to get speed. + // In visual tests we see that Hamming-1 is not as good as + // Lanczos-2, however it is about 40% faster, and Lanczos-2 itself is // about 30% faster than Lanczos-3. The use of Hamming-1 has been deemed - // an acceptable trade-off between quality and speed. + // an unacceptable trade-off between quality and speed due to the limited + // pixel space it operates in, so we pick Lanczos-2 here. case ImageOperations::RESIZE_BETTER: - return ImageOperations::RESIZE_HAMMING1; + return ImageOperations::RESIZE_LANCZOS2; default: return ImageOperations::RESIZE_LANCZOS3; } -- cgit v1.2.3