做网站 用什么建站软件好,wordpress 少数派,兰州优化公司哪个好,建筑清单网看完本文的标题#xff0c;可能有人要打我。你说黑白的老照片不好吗#xff1f;非要说什么遗像#xff0c;我现在就把你变成遗像#xff01;好了#xff0c;言归正传。我想大部分人都用过美颜相机或者剪映等软件吧#xff0c;它们的滤镜功能是如何实现的#xff0c;有人…看完本文的标题可能有人要打我。你说黑白的老照片不好吗非要说什么遗像我现在就把你变成遗像好了言归正传。我想大部分人都用过美颜相机或者剪映等软件吧它们的滤镜功能是如何实现的有人想过吗难道要使用Java/Kotlin遍历Bitmap然后处理到手机发烫吗学过计算机图形学的应该知道图片或视频的图像数据的最小单位是像素px。视频编码H.264的YUV数据不也是视频像素数据嘛只不过有很多帧。
代码实现
本篇文章我来教大家简单的处理图像中一个个的像素点的色值从而达到改变图片风格的效果。首先我们创建一个Native C项目。 然后我们需要写个简单的xml布局。
?xml version1.0 encodingutf-8?androidx.constraintlayout.widget.ConstraintLayoutxmlns:androidhttp://schemas.android.com/apk/res/androidxmlns:apphttp://schemas.android.com/apk/res-autoxmlns:toolshttp://schemas.android.com/toolsandroid:layout_widthmatch_parentandroid:layout_heightmatch_parenttools:context.MainActivityImageViewandroid:idid/iv_displayandroid:layout_widthwrap_contentandroid:layout_heightwrap_contentapp:layout_constraintBottom_toBottomOfparentapp:layout_constraintEnd_toEndOfparentapp:layout_constraintStart_toStartOfparentapp:layout_constraintTop_toTopOfparent /Buttonandroid:idid/btnPicProcessandroid:layout_widthmatch_parentandroid:layout_heightwrap_contentapp:layout_constraintEnd_toEndOfparentapp:layout_constraintStart_toStartOfparentapp:layout_constraintBottom_toBottomOfparentandroid:text黑白//androidx.constraintlayout.widget.ConstraintLayout接下来我们需要实现Activity的代码了。注意这里有个external方法它相当于java中的带native关键字的方法只不过这是kotlin的写法。在handleBitmap()方法中调用底层方法处理图像。就这么一个简单的流程因为我们把图像处理的逻辑全部都放到c底层代码中了。之所以把图像处理的逻辑全权交给C的原因我想大家应该都知道了IO是非常耗时的而两层循环的时间复杂度是O(n²)。那就是java使用jni跟c频繁通信会大量调输入输出流时间都损耗在bitmap的setPixels方法上了。那还不如你处理好了给我结果就好了我不需要关心过程。
package com.dorachat.myapplicationimport android.graphics.Bitmap
import android.graphics.BitmapFactory
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.dorachat.myapplication.databinding.ActivityMainBindingclass MainActivity : AppCompatActivity() {private lateinit var binding: ActivityMainBindingoverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)binding ActivityMainBinding.inflate(layoutInflater)setContentView(binding.root)val bitmap BitmapFactory.decodeResource(resources, R.drawable.pic)binding.ivDisplay.setImageBitmap(bitmap)binding.btnPicProcess.setOnClickListener {binding.ivDisplay.setImageBitmap(handleBitmap(bitmap))}}/*** jni处理图片。*/private fun handleBitmap(bitmap: Bitmap) : Bitmap {val bmp bitmap.copy(Bitmap.Config.ARGB_8888, true);nativeProcessBitmap(bmp);return bmp;}/*** 黑白特效调用native底层方法。*/external fun nativeProcessBitmap(bitmap: Bitmap)companion object {// Used to load the myapplication library on application startup.init {System.loadLibrary(myapplication)}}
}我们再来看下CMakeLists.txt的代码注意target_link_libraries中要链接jnigraphics。
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html.
# For more examples on how to use CMake, see https://github.com/android/ndk-samples.# Sets the minimum CMake version required for this project.
cmake_minimum_required(VERSION 3.22.1)# Declares the project name. The project name can be accessed via ${ PROJECT_NAME},
# Since this is the top level CMakeLists.txt, the project name is also accessible
# with ${CMAKE_PROJECT_NAME} (both CMake variables are in-sync within the top level
# build script scope).
project(myapplication)# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.
#
# In this top level CMakeLists.txt, ${CMAKE_PROJECT_NAME} is used to define
# the target library name; in the sub-modules CMakeLists.txt, ${PROJECT_NAME}
# is preferred for the same purpose.
#
# In order to load a library into your app from Java/Kotlin, you must call
# System.loadLibrary() and pass the name of the library defined here;
# for GameActivity/NativeActivity derived applications, the same library name must be
# used in the AndroidManifest.xml file.
add_library(${CMAKE_PROJECT_NAME} SHARED# List C/C source files with relative paths to this CMakeLists.txt.native-lib.cpp)# Specifies libraries CMake should link to your target library. You
# can link libraries from various origins, such as libraries defined in this
# build script, prebuilt third-party libraries, or Android system libraries.
target_link_libraries(${CMAKE_PROJECT_NAME}# List libraries link to the target libraryandroidlogjnigraphics)最后就是我们最最重要的底层代码了。通过调用AndroidBitmap_getInfo来读取图片像素数据并将其保存在AndroidBitmapInfo中。AndroidBitmap_lockPixels 是 Android Native Development Kit (NDK) 中的一个函数用于锁定一个 android.graphics.Bitmap 对象的像素数据以便在 Native 代码中进行像素级别的操作。这个函数允许在 C 或 C 代码中直接访问 Android 应用中的位图像素数据以便进行图像处理、渲染或其他图像相关的操作。最后记得调用AndroidBitmap_unlockPixels解锁。至于为什么是(RGB)/3这个问题要问我为什么这么算我能力有限教不了你们你得问计算机图像处理学的专家哈哈。当将彩色图像转换为黑白图像时通常采用灰度化的方法即将红、绿、蓝三个通道的数值取平均值以获得灰度图像。因此将RGB图像转换为黑白图像时每个像素的灰度值通常是红、绿、蓝通道值的平均值即(RGB)/3。
#include jni.h
#include string
#include stdio.h
#include pthread.h
#include unistd.h
#include android/bitmap.h#define MAKE_RGB565(r, g, b) ((((r) 3) 11) | (((g) 2) 5) | ((b) 3))
#define MAKE_ARGB(a, r, g, b) ((a0xff)24) | ((r0xff)16) | ((g0xff)8) | (b0xff)#define RGB565_R(p) ((((p) 0xF800) 11) 3)
#define RGB565_G(p) ((((p) 0x7E0 ) 5) 2)
#define RGB565_B(p) ( ((p) 0x1F ) 3)#define RGB8888_A(p) (p (0xff24) 24 )
#define RGB8888_R(p) (p (0xff16) 16 )
#define RGB8888_G(p) (p (0xff8) 8 )
#define RGB8888_B(p) (p (0xff) )#define RGBA_A(p) (((p) 0xFF000000) 24)
#define RGBA_R(p) (((p) 0x00FF0000) 16)
#define RGBA_G(p) (((p) 0x0000FF00) 8)
#define RGBA_B(p) ((p) 0x000000FF)
#define MAKE_RGBA(r, g, b, a) (((a) 24) | ((r) 16) | ((g) 8) | (b))extern C JNIEXPORT void JNICALL
Java_com_dorachat_myapplication_MainActivity_nativeProcessBitmap(JNIEnv *env,jobject instance,jobject bitmap) {if (bitmap NULL) {return;}AndroidBitmapInfo bitmapInfo;memset(bitmapInfo, 0, sizeof(bitmapInfo));// Need add jnigraphics into target_link_libraries in CMakeLists.txtAndroidBitmap_getInfo(env, bitmap, bitmapInfo);// Lock the bitmap to get the buffervoid *pixels NULL;int res AndroidBitmap_lockPixels(env, bitmap, pixels);// From top to bottomint x 0, y 0;for (y 0; y bitmapInfo.height; y) {// From left to rightfor (x 0; x bitmapInfo.width; x) {int a 0, r 0, g 0, b 0;void *pixel NULL;// Get each pixel by formatif (bitmapInfo.format ANDROID_BITMAP_FORMAT_RGBA_8888) {pixel ((uint32_t *) pixels) y * bitmapInfo.width x;int r, g, b;uint32_t v *((uint32_t *) pixel);r RGB8888_R(v);g RGB8888_G(v);b RGB8888_B(v);int sum r g b;*((uint32_t *) pixel) MAKE_ARGB(0xff, sum / 3, sum / 3, sum / 3);} else if (bitmapInfo.format ANDROID_BITMAP_FORMAT_RGB_565) {pixel ((uint16_t *) pixels) y * bitmapInfo.width x;int r, g, b;uint16_t v *((uint16_t *) pixel);r RGB565_R(v);g RGB565_G(v);b RGB565_B(v);int sum r g b;*((uint16_t *) pixel) MAKE_RGB565(sum / 3, sum / 3, sum / 3);}}}AndroidBitmap_unlockPixels(env, bitmap);
}效果演示
知道你们喜欢清纯的来了。最后不忘留个赞吧。
