本文介绍如何在iOS应用中使用GPUImage库为UIImage添加多个滤镜效果，并提供了具体的代码示例。此外，还讨论了如何正确地切换不同的滤镜效果。
from: http://www.scriptscoop.net/t/174138f67b0f/ios-how-to-add-multiple-filters-to-uiimage-gpuimage.html
I noticed a lot of people asking questions about linking filters with GPUImage. I can't quite figure out how to do it succinctly. Finally got it working tonight. Just wanted to share my code so people can link to the solution.
1 answer
By chrisallick
UIImage *faceImage = [UIImage imageNamed:@"469453586_640.jpg"]; UIImageView *face = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, faceImage.size.width/2.0, faceImage.size.height/2.0)]; [face setImage:faceImage]; [self.view addSubview:face]; GPUImagePicture *stillImageSource = [[GPUImagePicture alloc] initWithImage:faceImage]; GPUImageBrightnessFilter *brightnessFilter = [[GPUImageBrightnessFilter alloc] init]; [brightnessFilter setBrightness:.15]; GPUImageGrayscaleFilter *grayscaleFilter = [[GPUImageGrayscaleFilter alloc] init]; GPUImagePosterizeFilter *posterizeFilter = [[GPUImagePosterizeFilter alloc] init]; [posterizeFilter setColorLevels:1]; [stillImageSource addTarget:brightnessFilter]; [brightnessFilter addTarget:grayscaleFilter]; [grayscaleFilter addTarget:posterizeFilter]; // these need to be changed if you change the order of your filters // [brightnessFilter useNextFrameForImageCapture]; // [grayscaleFilter useNextFrameForImageCapture]; [posterizeFilter useNextFrameForImageCapture]; [stillImageSource processImage]; [face setImage: [posterizeFilter imageFromCurrentFramebuffer]];
2 similar answers β
By ophychius
I have an app that sort of does the same, and what I do is that I keep my baseImage at hand, and once I am done applying the filter and showing the image with filter I reset everything. The moment a user selects a different filter I use the baseImage again to create the new filtered image and show it.
So in this example you could for example move the [sourcePicture removeAllTargets]; to right after this [self.view addSubview:filterView];
That saves you work when you want to apply a new filter. Also, there is a quicker (dirtier way to filter a picture when you are working with an image that already exists. I got this from the documentation that came with GPUImage and it works like a charm.
GPUImageSketchFilter *stillImageFilter2 = [[GPUImageSketchFilter alloc] init]; tmp = [stillImageFilter2 imageByFilteringImage:[self baseImage]]; [self.imageView setImage: tmp]; tmp = nil;
Hope it helps you on your way.
By user4211235
You can sometimes get hints/code for your apps via the open source repo for the Rally App Catalog. For your example, there is available source code for the Release Planning App. Reviewing the source code, you can see that the Filter Picker is defined by the following requirement defined in the source:
Rally.ui.gridboard.plugin.GridBoardCustomFilterControl
And this is incorporated into the board by adding its plugin to the board configuration.
It's tempting to add this to a Simple Grid example, exactly as the Release planning board does, which I tried doing as follows:
<!DOCTYPE html> <html> <head> <title>Rally Example: Simple Board</title> <script type="text/javascript" src="/apps/2.0rc3/sdk.js"></script> <script type="text/javascript"> Rally.onReady(function () { Ext.define('Rally.example.SimpleBoard', { extend: 'Rally.app.App', requires: [ 'Rally.ui.gridboard.plugin.GridBoardCustomFilterControl' ], launch: function() { this.add({ xtype: 'rallycardboard', types: ['User Story'], attribute: 'ScheduleState', context: this.getContext(), readOnly: true, cardConfig: { showIconsAndHighlightBorder: false, editable: false }, plugins: [ { ptype: 'rallygridboardcustomfiltercontrol', filterChildren: false, filterControlConfig: { margin: '3 9 3 30', blackListFields: ['PortfolioItemType', 'Release'], whiteListFields: [this._milestonesAreEnabled() ? 'Milestones' : ''], modelNames: ['HierarchicalRequirement'] } } ] }); } }); Rally.launchApp('Rally.example.SimpleBoard', { name:"Rally Example: Simple Board", parentRepos:"" }); }); </script> <style type="text/css"> .app { /* Add app styles here */ } </style> </head> <body> </body> </html>
However, if you try to load the app in this way, you'll get a 404 when it looks for the Rally.ui.gridboard.plugin.GridBoardCustomFilterControlclass.
Looking at the AppSDK2.0rc3 docs, this plugin does not appear to be available under the Rally.ui.cardboard.plugins.* tree that's bundled into the SDK. See screenshot here:
AppSDK2.0rc3 screenshot excerpt:
Nor does it appear that the Rally.ui.gridboard.plugin.* tree is bundled into the AppSDK. It is likely that the class is however, available to the Rally UI via a different javascript bundle (non-public) that the Rally developers use.
Perhaps it would be feasible for Rally Engineering to bundle this plugin into the AppSDK so that customer developers could use it - perhaps file a Feature Request on Rally Ideas or something like that to see if this is achievable.
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