iOS: Feather with glow/shadow effect on uiimage - ios

Question

I am trying to find a way to apply feather effect with shadow around the UIImage, not UIImageView I have in iOS, I couldn't find any perfect solution yet. I have an idea that it might be done by masking, but I am very new to CoreGraphics.
If anyone can help.
Thanks.

Answer 1

OK so:
I was looking for same thing, but unfortunately with no luck.
I decided to create my own feather(ing) code.
add this code to the UIImage extension, and then call [image featherImageWithDepth:4], 4 is just example.
Try to keep depth as low as possible.
//==============================================================================
- (UIImage*)featherImageWithDepth:(int)featherDepth {
// First get the image into your data buffer
CGImageRef imageRef = [self CGImage];
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = (unsigned char*) calloc(height * width * 4, sizeof(unsigned char));
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(rawData, width, height,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
// Now your rawData contains the image data in the RGBA8888 pixel format.
NSUInteger byteIndex = 0;
NSUInteger rawDataCount = width*height;
for (int i = 0 ; i < rawDataCount ; ++i, byteIndex += bytesPerPixel) {
NSInteger alphaIndex = byteIndex + 3;
if (rawData[alphaIndex] > 100) {
for (int row = 1; row <= featherDepth; row++) {
if (testBorderLayer((long)alphaIndex,
rawData,
(long)rawDataCount,
(long)width,
(long)height,
row)) {
int destinationAlpha = 255 / (featherDepth+1) * (row + 1);
double alphaDiv = (double)destinationAlpha / (double)rawData[alphaIndex];
rawData[alphaIndex] = destinationAlpha;
rawData[alphaIndex-1] = (double)rawData[alphaIndex-1] * alphaDiv;
rawData[alphaIndex-2] = (double)rawData[alphaIndex-2] * alphaDiv;
rawData[alphaIndex-3] = (double)rawData[alphaIndex-3] * alphaDiv;
// switch (row) {
// case 1:
// rawData[alphaIndex-1] = 255;
// rawData[alphaIndex-2] = 0;
// rawData[alphaIndex-3] = 0;
// break;
// case 2:
// rawData[alphaIndex-1] = 0;
// rawData[alphaIndex-2] = 255;
// rawData[alphaIndex-3] = 0;
// break;
// case 3:
// rawData[alphaIndex-1] = 0;
// rawData[alphaIndex-2] = 0;
// rawData[alphaIndex-3] = 255;
// break;
// case 4:
// rawData[alphaIndex-1] = 127;
// rawData[alphaIndex-2] = 127;
// rawData[alphaIndex-3] = 0;
// break;
// case 5:
// rawData[alphaIndex-1] = 127;
// rawData[alphaIndex-2] = 0;
// rawData[alphaIndex-3] = 127;
// case 6:
// rawData[alphaIndex-1] = 0;
// rawData[alphaIndex-2] = 127;
// rawData[alphaIndex-3] = 127;
// break;
// default:
// break;
// }
break;
}
}
}
}
CGImageRef newCGImage = CGBitmapContextCreateImage(context);
UIImage *result = [UIImage imageWithCGImage:newCGImage scale:[self scale] orientation:UIImageOrientationUp];
CGImageRelease(newCGImage);
CGContextRelease(context);
free(rawData);
return result;
}
//==============================================================================
bool testBorderLayer(long byteIndex,
unsigned char *imageData,
long dataSize,
long pWidth,
long pHeight,
int border) {
int width = border * 2 + 1;
int height = width - 2;
// run thru border pixels
// |-|
// | |
// |-|
//top,bot - hor
for (int i = 1; i < width - 1; i++) {
long topIndex = byteIndex + 4 * ( - border * pWidth - border + i);
long botIndex = byteIndex + 4 * ( border * pWidth - border + i);
long destColl = byteIndex/4 % pWidth - border + i;
if (destColl > 1 && destColl < pWidth) {
if (testPoint(topIndex, imageData, dataSize) ||
testPoint(botIndex, imageData, dataSize)) {
return true;
}
}
}
//left,right - ver
if (byteIndex / 4 % pWidth < pWidth - border - 1) {
for (int k = 0; k < height; k++) {
long rightIndex = byteIndex + 4 * ( border - (border) * pWidth + pWidth * k);
if (testPoint(rightIndex, imageData, dataSize)) {
return true;
}
}
}
if (byteIndex / 4 % pWidth > border) {
for (int k = 0; k < height; k++) {
long leftIndex = byteIndex + 4 * ( - border - (border) * pWidth + pWidth * k);
if (testPoint(leftIndex, imageData, dataSize)) {
return true;
}
}
}
return false;
}
//==============================================================================
bool testPoint(long pointIndex, unsigned char *imageData, long dataSize) {
if (pointIndex >= 0 && pointIndex < dataSize * 4 - 1 &&
imageData[pointIndex] < 30) {
return true;
}
return false;
}
//==============================================================================
Sorry for rare commenting ;)

Answer 2

I suggest looking at this CIFilter list put out by apple, they got some pretty decent filters.
/reference/CoreImageFilterReference
And also check out GPUImage.
https://github.com/BradLarson/GPUImage