我编写了一种使用亮度因子和对比度因子过滤图像的方法，如下所示:
- (UIImage*)image:(UIImage*)image withBrightness:(float)brightness contrast:(float)contrast{
GPUImagePicture *imagePicture = [[GPUImagePicture alloc] initWithImage:image];
GPUImageBrightnessFilter *brightnessFilter = [[GPUImageBrightnessFilter alloc] init];
GPUImageContrastFilter *contrastFilter = [[GPUImageContrastFilter alloc] init];
[imagePicture addTarget:brightnessFilter];
[brightnessFilter addTarget:contrastFilter];
brightnessFilter.brightness = brightness; // set brightness
contrastFilter.contrast = contrast; // set contrast
[imagePicture processImage];
UIImage *filteredImage = [contrastFilter imageFromCurrentlyProcessedOutput];
return filteredImage;
}
调用此实现将引发错误:
<Error>: CGContextDrawImage: invalid context 0x0。如何使用GPUImage正确实现亮度和对比度调整？
最佳答案
您可能应该创建一个组过滤器，请检查此示例代码
GPUImageFilterGroup *groupFilter = [[GPUImageFilterGroup alloc]init];
[groupFilter addTarget:edit.currentFilter];
//create a brightness filter
GPUImageBrightnessFilter *brightnessFilter = [[GPUImageBrightnessFilter alloc]init];
[brightnessFilter setBrightness:brightnessValue];
//create a contrast filter
GPUImageContrastFilter *contrastFilter = [[GPUImageContrastFilter alloc]init];
[contrastFilter setContrast:contrastValue];
//create a exposure filter
GPUImageExposureFilter *exposureFilter =[[GPUImageExposureFilter alloc]init];
[exposureFilter setExposure:exposureValue];
//add brightness,contrast,exposure filters to group filter
[groupFilter addFilter:brightnessFilter];
[groupFilter addFilter:contrastFilter];
[groupFilter addFilter:exposureFilter];
[edit.currentFilter addTarget:brightnessFilter];
[brightnessFilter addTarget: contrastFilter];
[contrastFilter addTarget: exposureFilter];
//setting initial and terminal filters
[(GPUImageFilterGroup *) groupFilter setInitialFilters:[NSArray arrayWithObject:edit.currentFilter]];
[(GPUImageFilterGroup *) groupFilter setTerminalFilter:exposureFilter];
//apply it to the GPUImagePicture
关于ios - 如何通过GPUImage调整图像的亮度和对比度？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19134112/