mirror of
https://github.com/hoernschen/dendrite.git
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249 lines
8.7 KiB
Go
249 lines
8.7 KiB
Go
// Copyright 2017 Vector Creations Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package thumbnailer
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import (
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"context"
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"fmt"
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"math"
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"os"
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"path/filepath"
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"sync"
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"github.com/matrix-org/dendrite/common/config"
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"github.com/matrix-org/dendrite/mediaapi/storage"
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"github.com/matrix-org/dendrite/mediaapi/types"
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log "github.com/sirupsen/logrus"
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)
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type thumbnailFitness struct {
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isSmaller int
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aspect float64
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size float64
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methodMismatch int
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fileSize types.FileSizeBytes
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}
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// thumbnailTemplate is the filename template for thumbnails
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const thumbnailTemplate = "thumbnail-%vx%v-%v"
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// GetThumbnailPath returns the path to a thumbnail given the absolute src path and thumbnail size configuration
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func GetThumbnailPath(src types.Path, config types.ThumbnailSize) types.Path {
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srcDir := filepath.Dir(string(src))
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return types.Path(filepath.Join(
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srcDir,
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fmt.Sprintf(thumbnailTemplate, config.Width, config.Height, config.ResizeMethod),
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))
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}
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// SelectThumbnail compares the (potentially) available thumbnails with the desired thumbnail and returns the best match
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// The algorithm is very similar to what was implemented in Synapse
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// In order of priority unless absolute, the following metrics are compared; the image is:
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// * the same size or larger than requested
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// * if a cropped image is desired, has an aspect ratio close to requested
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// * has a size close to requested
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// * if a cropped image is desired, prefer the same method, if scaled is desired, absolutely require scaled
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// * has a small file size
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// If a pre-generated thumbnail size is the best match, but it has not been generated yet, the caller can use the returned size to generate it.
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// Returns nil if no thumbnail matches the criteria
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func SelectThumbnail(desired types.ThumbnailSize, thumbnails []*types.ThumbnailMetadata, thumbnailSizes []config.ThumbnailSize) (*types.ThumbnailMetadata, *types.ThumbnailSize) {
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var chosenThumbnail *types.ThumbnailMetadata
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var chosenThumbnailSize *types.ThumbnailSize
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bestFit := newThumbnailFitness()
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for _, thumbnail := range thumbnails {
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if desired.ResizeMethod == types.Scale && thumbnail.ThumbnailSize.ResizeMethod != types.Scale {
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continue
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}
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fitness := calcThumbnailFitness(thumbnail.ThumbnailSize, thumbnail.MediaMetadata, desired)
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if isBetter := fitness.betterThan(bestFit, desired.ResizeMethod == types.Crop); isBetter {
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bestFit = fitness
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chosenThumbnail = thumbnail
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}
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}
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for _, thumbnailSize := range thumbnailSizes {
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if desired.ResizeMethod == types.Scale && thumbnailSize.ResizeMethod != types.Scale {
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continue
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}
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fitness := calcThumbnailFitness(types.ThumbnailSize(thumbnailSize), nil, desired)
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if isBetter := fitness.betterThan(bestFit, desired.ResizeMethod == types.Crop); isBetter {
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bestFit = fitness
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chosenThumbnailSize = (*types.ThumbnailSize)(&thumbnailSize)
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}
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}
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return chosenThumbnail, chosenThumbnailSize
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}
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// getActiveThumbnailGeneration checks for active thumbnail generation
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func getActiveThumbnailGeneration(dst types.Path, _ types.ThumbnailSize, activeThumbnailGeneration *types.ActiveThumbnailGeneration, maxThumbnailGenerators int, logger *log.Entry) (isActive bool, busy bool, errorReturn error) {
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// Check if there is active thumbnail generation.
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activeThumbnailGeneration.Lock()
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defer activeThumbnailGeneration.Unlock()
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if activeThumbnailGenerationResult, ok := activeThumbnailGeneration.PathToResult[string(dst)]; ok {
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logger.Info("Waiting for another goroutine to generate the thumbnail.")
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// NOTE: Wait unlocks and locks again internally. There is still a deferred Unlock() that will unlock this.
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activeThumbnailGenerationResult.Cond.Wait()
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// Note: either there is an error or it is nil, either way returning it is correct
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return false, false, activeThumbnailGenerationResult.Err
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}
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// Only allow thumbnail generation up to a maximum configured number. Above this we fall back to serving the
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// original. Or in the case of pre-generation, they maybe get generated on the first request for a thumbnail if
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// load has subsided.
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if len(activeThumbnailGeneration.PathToResult) >= maxThumbnailGenerators {
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return false, true, nil
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}
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// No active thumbnail generation so create one
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activeThumbnailGeneration.PathToResult[string(dst)] = &types.ThumbnailGenerationResult{
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Cond: &sync.Cond{L: activeThumbnailGeneration},
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}
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return true, false, nil
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}
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// broadcastGeneration broadcasts that thumbnail generation completed and the error to all waiting goroutines
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// Note: This should only be called by the owner of the activeThumbnailGenerationResult
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func broadcastGeneration(dst types.Path, activeThumbnailGeneration *types.ActiveThumbnailGeneration, _ types.ThumbnailSize, errorReturn error, logger *log.Entry) {
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activeThumbnailGeneration.Lock()
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defer activeThumbnailGeneration.Unlock()
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if activeThumbnailGenerationResult, ok := activeThumbnailGeneration.PathToResult[string(dst)]; ok {
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logger.Info("Signalling other goroutines waiting for this goroutine to generate the thumbnail.")
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// Note: errorReturn is a named return value error that is signalled from here to waiting goroutines
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activeThumbnailGenerationResult.Err = errorReturn
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activeThumbnailGenerationResult.Cond.Broadcast()
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}
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delete(activeThumbnailGeneration.PathToResult, string(dst))
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}
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func isThumbnailExists(
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ctx context.Context,
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dst types.Path,
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config types.ThumbnailSize,
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mediaMetadata *types.MediaMetadata,
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db *storage.Database,
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logger *log.Entry,
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) (bool, error) {
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thumbnailMetadata, err := db.GetThumbnail(
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ctx, mediaMetadata.MediaID, mediaMetadata.Origin,
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config.Width, config.Height, config.ResizeMethod,
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)
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if err != nil {
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logger.Error("Failed to query database for thumbnail.")
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return false, err
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}
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if thumbnailMetadata != nil {
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return true, nil
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}
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// Note: The double-negative is intentional as os.IsExist(err) != !os.IsNotExist(err).
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// The functions are error checkers to be used in different cases.
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if _, err = os.Stat(string(dst)); !os.IsNotExist(err) {
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// Thumbnail exists
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return true, nil
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}
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return false, nil
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}
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// init with worst values
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func newThumbnailFitness() thumbnailFitness {
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return thumbnailFitness{
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isSmaller: 1,
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aspect: math.Inf(1),
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size: math.Inf(1),
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methodMismatch: 0,
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fileSize: types.FileSizeBytes(math.MaxInt64),
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}
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}
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func calcThumbnailFitness(size types.ThumbnailSize, metadata *types.MediaMetadata, desired types.ThumbnailSize) thumbnailFitness {
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dW := desired.Width
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dH := desired.Height
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tW := size.Width
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tH := size.Height
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fitness := newThumbnailFitness()
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// In all cases, a larger metric value is a worse fit.
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// compare size: thumbnail smaller is true and gives 1, larger is false and gives 0
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fitness.isSmaller = boolToInt(tW < dW || tH < dH)
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// comparison of aspect ratios only makes sense for a request for desired cropped
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fitness.aspect = math.Abs(float64(dW*tH - dH*tW))
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// compare sizes
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fitness.size = math.Abs(float64((dW - tW) * (dH - tH)))
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// compare resize method
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fitness.methodMismatch = boolToInt(size.ResizeMethod != desired.ResizeMethod)
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if metadata != nil {
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// file size
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fitness.fileSize = metadata.FileSizeBytes
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}
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return fitness
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}
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func boolToInt(b bool) int {
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if b {
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return 1
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}
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return 0
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}
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func (a thumbnailFitness) betterThan(b thumbnailFitness, desiredCrop bool) bool {
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// preference means returning -1
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// prefer images that are not smaller
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// e.g. isSmallerDiff > 0 means b is smaller than desired and a is not smaller
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if a.isSmaller > b.isSmaller {
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return false
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} else if a.isSmaller < b.isSmaller {
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return true
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}
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// prefer aspect ratios closer to desired only if desired cropped
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// only cropped images have differing aspect ratios
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// desired scaled only accepts scaled images
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if desiredCrop {
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if a.aspect > b.aspect {
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return false
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} else if a.aspect < b.aspect {
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return true
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}
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}
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// prefer closer in size
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if a.size > b.size {
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return false
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} else if a.size < b.size {
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return true
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}
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// prefer images using the same method
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// e.g. methodMismatchDiff > 0 means b's method is different from desired and a's matches the desired method
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if a.methodMismatch > b.methodMismatch {
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return false
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} else if a.methodMismatch < b.methodMismatch {
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return true
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}
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// prefer smaller files
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if a.fileSize > b.fileSize {
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return false
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} else if a.fileSize < b.fileSize {
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return true
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}
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return false
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}
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