A category for Sparrow that allows erasing of a SPRenderTexture.
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// | |
// SPRenderTexture+Erase.h | |
// Sparrow | |
// | |
// Created by Shilo White on 11/10/11. | |
// Copyright (c) 2011 Shilocity Productions. All rights reserved. | |
// | |
#import "SPRenderTexture.h" | |
@class SPDisplayObject; | |
@class SPRectangle; | |
@interface SPRenderTexture (Erase) | |
- (void)eraseWithObject:(SPDisplayObject *)object; | |
- (void)eraseWithRectangle:(SPRectangle *)rectangle; | |
- (void)eraseWithEllipseInRectangle:(SPRectangle *)rectangle; | |
- (void)eraseWithDrawingBlock:(SPDrawingBlock)block; | |
- (float)averagePixelAlphaForRectangle:(SPRectangle *)rectangle; | |
@end |
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// | |
// SPRenderTexture+Erase.m | |
// Sparrow | |
// | |
// Created by Shilo White on 11/10/11. | |
// Copyright (c) 2011 Shilocity Productions. All rights reserved. | |
// | |
#import "SPRenderTexture+Erase.h" | |
#import "SPDisplayObject.h" | |
#import "SPRectangle.h" | |
#import "SPImage.h" | |
#import "SPRenderSupport.h" | |
#import "SPMacros.h" | |
@interface SPRenderTexture (Methods) | |
- (void)renderToFramebuffer:(SPDrawingBlock)block; | |
@end | |
@interface SPImage (Erase) | |
- (void)renderAsEraser:(SPRenderSupport *)support; | |
@end | |
@implementation SPImage (Erase) | |
- (void)renderAsEraser:(SPRenderSupport *)support { | |
static float texCoords[8]; | |
static uint colors[4]; | |
float alpha = self.alpha; | |
[support bindTexture:mTexture]; | |
[mTexture adjustTextureCoordinates:mTexCoords saveAtTarget:texCoords numVertices:4]; | |
for (int i=0; i<4; ++i) | |
colors[i] = [support convertColor:mVertexColors[i] alpha:alpha]; | |
SPRectangle *frame = mTexture.frame; | |
if (frame) { | |
glTranslatef(-frame.x, -frame.y, 0.0f); | |
glScalef(mTexture.width / frame.width, mTexture.height / frame.height, 1.0f); | |
} | |
glEnableClientState(GL_TEXTURE_COORD_ARRAY); | |
glEnableClientState(GL_VERTEX_ARRAY); | |
glEnableClientState(GL_COLOR_ARRAY); | |
glTexCoordPointer(2, GL_FLOAT, 0, texCoords); | |
glVertexPointer(2, GL_FLOAT, 0, mVertexCoords); | |
glColorPointer(4, GL_UNSIGNED_BYTE, 0, colors); | |
glBlendFunc(GL_ZERO, GL_ONE_MINUS_SRC_COLOR); | |
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); | |
glDisableClientState(GL_TEXTURE_COORD_ARRAY); | |
glDisableClientState(GL_VERTEX_ARRAY); | |
glDisableClientState(GL_COLOR_ARRAY); | |
} | |
@end | |
@implementation SPRenderTexture (Erase) | |
- (void)eraseWithObject:(SPDisplayObject *)object { | |
[self renderToFramebuffer:^ | |
{ | |
BOOL isImage = [object isKindOfClass:[SPImage class]]; | |
if (!isImage) glDisable(GL_BLEND); | |
glPushMatrix(); | |
[SPRenderSupport transformMatrixForObject:object]; | |
if (isImage) { | |
[(SPImage *)object renderAsEraser:mRenderSupport]; | |
} else { | |
float curAlpha = object.alpha; | |
object.alpha = 0; | |
[object render:mRenderSupport]; | |
object.alpha = curAlpha; | |
} | |
glPopMatrix(); | |
if (!isImage) glEnable(GL_BLEND); | |
}]; | |
} | |
- (void)eraseWithRectangle:(SPRectangle *)rectangle { | |
[self renderToFramebuffer:^ | |
{ | |
glDisable(GL_BLEND); | |
glPushMatrix(); | |
glEnableClientState(GL_VERTEX_ARRAY); | |
glEnableClientState(GL_COLOR_ARRAY); | |
glVertexPointer(2, GL_FLOAT, 0, (GLfloat[8]){0.0f, 0.0f, rectangle.width, 0.0f, 0.0f, rectangle.height, rectangle.width, rectangle.height}); | |
glColorPointer(4, GL_UNSIGNED_BYTE, 0, (GLuint[4]){0x0, 0x0, 0x0, 0x0}); | |
glTranslatef(rectangle.x, rectangle.y, 0.0f); | |
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); | |
glDisableClientState(GL_VERTEX_ARRAY); | |
glDisableClientState(GL_COLOR_ARRAY); | |
glPopMatrix(); | |
glEnable(GL_BLEND); | |
}]; | |
} | |
- (void)eraseWithEllipseInRectangle:(SPRectangle *)rectangle { | |
[self renderToFramebuffer:^ | |
{ | |
GLfloat vertices[724]; | |
GLuint colors[362]; | |
GLfloat widthRadius = rectangle.width/2; | |
GLfloat heightRadius = rectangle.height/2; | |
vertices[0] = widthRadius; | |
vertices[1] = heightRadius; | |
colors[0] = colors[361] = 0x0; | |
for (int i=0; i<360*2+1; i+=2) { | |
vertices[i+2] = cos(SP_D2R(i/2)) * widthRadius + widthRadius; | |
vertices[i+3] = sin(SP_D2R(i/2)) * heightRadius + heightRadius; | |
if (i<361 && i>1) colors[i] = colors[i-1] = 0x0; | |
} | |
glDisable(GL_BLEND); | |
glPushMatrix(); | |
glEnableClientState(GL_VERTEX_ARRAY); | |
glEnableClientState(GL_COLOR_ARRAY); | |
glVertexPointer(2, GL_FLOAT, 0, vertices); | |
glColorPointer(4, GL_UNSIGNED_BYTE, 0, colors); | |
glTranslatef(rectangle.x, rectangle.y, 0.0f); | |
glDrawArrays(GL_TRIANGLE_FAN, 0, 362); | |
glDisableClientState(GL_VERTEX_ARRAY); | |
glDisableClientState(GL_COLOR_ARRAY); | |
glPopMatrix(); | |
glEnable(GL_BLEND); | |
}]; | |
} | |
- (void)eraseWithDrawingBlock:(SPDrawingBlock)block { | |
[self renderToFramebuffer:^ | |
{ | |
glDisable(GL_BLEND); | |
glPushMatrix(); | |
block(); | |
glPopMatrix(); | |
glEnable(GL_BLEND); | |
}]; | |
} | |
- (float)averagePixelAlphaForRectangle:(SPRectangle *)rectangle { | |
__block float averageAlpha = 0; | |
[self renderToFramebuffer:^ | |
{ | |
int pixelCount = rectangle.width*rectangle.height; | |
int bufferLength = pixelCount*4; | |
unsigned char buffer[bufferLength]; | |
int totalAlpha = 0; | |
glReadPixels(rectangle.x, rectangle.y, rectangle.width, rectangle.height, GL_RGBA, GL_UNSIGNED_BYTE, &buffer); | |
for (int i=3; i<bufferLength; i+=4) { | |
totalAlpha += buffer[i]; | |
} | |
averageAlpha = (totalAlpha/pixelCount)/255.0f; | |
}]; | |
return averageAlpha; | |
} | |
@end |
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