Rotate GPUImageTiltShiftFilter - GPUImage

问题

I want a non-horizontal GPUImageTiltShiftFilter rotation. I want to rotate it to an arbitrary rotation angle. I also want the filter to be fast it can be rotated with a UI with a UIRotationGestureRecongizer.

How do I do this?

回答1:

Ah, figured it out!

Instead of modifying GPUImageTiltShiftFilter, make a new GPUImageFilterGroup as a modified version of GPUImageGaussianSelectiveBlurFilter to add rotation.

I added:

   uniform highp float rotation;

within kGPUImageSMTiltShiftFragmentShaderString, and I added the distanceFromCenter line to the main of GPUImageGaussianSelectiveBlurFilter to turn GPUImageGaussianSelectiveBlurFilter into a tilt shift with rotation:

 void main()
{
   lowp vec4 sharpImageColor = texture2D(inputImageTexture, textureCoordinate);
   lowp vec4 blurredImageColor = texture2D(inputImageTexture2, textureCoordinate2);

   highp vec2 textureCoordinateToUse = vec2(textureCoordinate2.x, (textureCoordinate2.y * aspectRatio + 0.5 - 0.5 * aspectRatio));

   highp float distanceFromCenter = abs((textureCoordinate2.x - excludeCirclePoint.x) * aspectRatio*cos(rotation) + (textureCoordinate2.y-excludeCirclePoint.y)*sin(rotation));

   gl_FragColor = mix(sharpImageColor, blurredImageColor, smoothstep(excludeCircleRadius - excludeBlurSize, excludeCircleRadius, distanceFromCenter));
 }

来源：https://stackoverflow.com/questions/16407840/rotate-gpuimagetiltshiftfilter-gpuimage