今天來學習一下一個簡單濾鏡使用的流程，通過調節亮度濾鏡來了解。先將GPUImage庫導入到項目中，引入頭文件"GPUImage.h"
一、創建亮度濾鏡對象
GPUImageBrightnessFilter *filter = [[GPUImageBrightnessFilter alloc] init]，經過alloc init之后，程序為我們創建了頂點數組以及幀緩沖區，紋理，并綁定為當前使用的對象。
1.為頂點著色添加屬性
首先我們來看一該濾鏡的頂點著色器字符串
attribute vec4 position; attribute vec4 inputTextureCoordinate; varying vec2 textureCoordinate; void main() { gl_Position = position; textureCoordinate = inputTextureCoordinate.xy; }
我們了解到該頂點有2個需要添加的屬性position，inputTextureCoordinate.我們需要在程序中添加這2個屬性，通過下列方法來添加
- (void)initializeAttributes;{ [filterPRogram addAttribute:@"position"]; [filterProgram addAttribute:@"inputTextureCoordinate"]; // Override this, calling back to this super method, in order to add new attributes to your vertex shader}
2.片段著色提供uniform
varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform lowp float brightness; void main() { lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate); gl_FragColor = vec4((textureColor.rgb + vec3(brightness)), textureColor.w); }
brightnessUniform = [filterProgram uniformIndex:@"brightness"]
filterInputTextureUniform = [filterProgram uniformIndex:@"inputImageTexture"]
3.啟用頂點數組
glEnableVertexAttribArray(filterPositionAttribute);
glEnableVertexAttribArray(filterTextureCoordinateAttribute)
4.創建紋理
- (void)generateTexture;{ glActiveTexture(GL_TEXTURE1); glGenTextures(1, &_texture); glBindTexture(GL_TEXTURE_2D, _texture); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, _textureOptions.minFilter); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, _textureOptions.magFilter); // This is necessary for non-power-of-two textures glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, _textureOptions.wrapS); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, _textureOptions.wrapT); // TODO: Handle mipmaps}
5.創建幀緩沖區glGenFramebuffers(1, &framebuffer)
6.幀緩沖綁定紋理
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _texture, 0);
二、設置亮度值
filter.brightness = value
三、設置紋理尺寸
[filter forceProcessingAtSize:image.size]
四、創建GPUImagePicture對象
GPUImagePicture *pic = [[GPUImagePicture alloc] initWithImage:image]
五、向創建好的GPUImagePicture對象添加target
六，處理圖像
[pic processImage]
進行圖像渲染并繪制
glClearColor(backgroundColorRed, backgroundColorGreen, backgroundColorBlue, backgroundColorAlpha); glClear(GL_COLOR_BUFFER_BIT); glActiveTexture(GL_TEXTURE2); glBindTexture(GL_TEXTURE_2D, [firstInputFramebuffer texture]); glUniform1i(filterInputTextureUniform, 2); glVertexAttribPointer(filterPositionAttribute, 2, GL_FLOAT, 0, 0, vertices); glVertexAttribPointer(filterTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, textureCoordinates); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
七、[filter useNextFrameForImageCapture]
八、獲取處理后的圖像
image ＝ [filter imageFromCurrentFramebuffer]
GPUImageBrightnessFilter *filter = [[GPUImageBrightnessFilter alloc] init]; filter.brightness = value; [filter forceProcessingAtSize:image.size]; GPUImagePicture *pic = [[GPUImagePicture alloc] initWithImage:image]; [pic addTarget:filter]; [pic processImage]; [filter useNextFrameForImageCapture]; image ＝ [filter imageFromCurrentFramebuffer];
新聞熱點
疑難解答
