iOS濾鏡實現之Nashville【instagram】

Nashville是Instagram衆多濾鏡中最驚豔的一款，獨特的奶昔色調賦予照片童話般的惟美感受。
適用範圍：營造浪漫惟美的感受。
的確如此啊
有2張輸入圖像

頂點着色
有2組座標
NSString *const kGPUImageTwoInputTextureVertexShaderString = SHADER_STRING

(
 attribute vec4 position;
//輸入的座標
 attribute vec4 inputTextureCoordinate;
 attribute vec4 inputTextureCoordinate2;
 //輸出的座標，與片斷着色器
 varying vec2 textureCoordinate;
 varying vec2 textureCoordinate2;
 
 void main() {
//告訴片斷着色器，我在處理哪些像素 gl_Position = position; textureCoordinate = inputTextureCoordinate.xy; textureCoordinate2 = inputTextureCoordinate2.xy; } );

片斷着色

NSString *const kFWNashvilleShaderString = SHADER_STRING
(
 precision lowp float; varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform sampler2D inputImageTexture2; void main() { vec3 texel = texture2D(inputImageTexture, textureCoordinate).rgb; texel = vec3( texture2D(inputImageTexture2, vec2(texel.r, .16666)).r, texture2D(inputImageTexture2, vec2(texel.g, .5)).g, texture2D(inputImageTexture2, vec2(texel.b, .83333)).b); gl_FragColor = vec4(texel, 1.0); } );

 

 初始化

- (id)init
{
    if (!(self = [super init]))
    {
        return nil;
    }
    
    UIImage *image = [UIImage imageNamed:@"nashvilleMap.png"];
    
    imageSource = [[GPUImagePicture alloc] initWithImage:image];
    FWFilter1 *filter = [[FWFilter1 alloc] init];
    
    [self addFilter:filter];
    [imageSource addTarget:filter atTextureLocation:1];
    [imageSource processImage];
    
    self.initialFilters = [NSArray arrayWithObjects:filter, nil];
    self.terminalFilter = filter;
    
    return self;
}

//
//  FWNashvilleFilter.h
//  FWMeituApp
//
//  Created by hzkmn on 16/1/8.
//  Copyright © 2016年 ForrestWoo co,.ltd. All rights reserved.
//

#import "GPUImageTwoInputFilter.h"

@interface FWFilter1 : GPUImageTwoInputFilter



@end

@interface FWNashvilleFilter : GPUImageFilterGroup
{
    GPUImagePicture *imageSource ;
}

@end

 

//
//  FWNashvilleFilter.m
//  FWMeituApp
//
//  Created by hzkmn on 16/1/8.
//  Copyright © 2016年 ForrestWoo co,.ltd. All rights reserved.
//

#import "FWNashvilleFilter.h"

NSString *const kFWNashvilleShaderString = SHADER_STRING
(
 precision lowp float;
 
 varying highp vec2 textureCoordinate;
 
 uniform sampler2D inputImageTexture;
 uniform sampler2D inputImageTexture2;
 
 void main()
 {
     vec3 texel = texture2D(inputImageTexture, textureCoordinate).rgb;
     texel = vec3(
                  texture2D(inputImageTexture2, vec2(texel.r, .16666)).r,
                  texture2D(inputImageTexture2, vec2(texel.g, .5)).g,
                  texture2D(inputImageTexture2, vec2(texel.b, .83333)).b);
     gl_FragColor = vec4(texel, 1.0);
 }
 );

@implementation FWFilter1

- (id)init;
{
    if (!(self = [super initWithFragmentShaderFromString:kFWNashvilleShaderString]))
    {
        return nil;
    }
    
    return self;
}

@end

@implementation FWNashvilleFilter

- (id)init
{
    if (!(self = [super init]))
    {
        return nil;
    }
    
    UIImage *image = [UIImage imageNamed:@"nashvilleMap.png"];
    
    imageSource = [[GPUImagePicture alloc] initWithImage:image];
    FWFilter1 *filter = [[FWFilter1 alloc] init];
    
    [self addFilter:filter];
    [imageSource addTarget:filter atTextureLocation:1];
    [imageSource processImage];
    
    self.initialFilters = [NSArray arrayWithObjects:filter, nil];
    self.terminalFilter = filter;
    
    return self;
}

@end

 

原圖

效果圖

完整項目代碼查看我在github

 

 咱們再來看幾組效果