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I am trying to create an image mask with kCGColorSpaceDisplayP3 colorspace to support the iPhone 7's wide color range.
I am able to create image mask correctly when using sRGB colorspace on iPhone 6 and earlier devices using iOS 10 and earlier iOS. But I have no clue where I am going wrong when creating colorspace using kCGColorSpaceDisplayP3:
CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceDisplayP3);
CGContextRef context = CGBitmapContextCreate(NULL, 320.0, 320.0, 32, 320.0*16, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapFloatComponents);
CGFloat radius = 10.0;
CGFloat components[] = {1.0,1.0,1.0,1.0, 1.0,1.0,1.0,1.0, 1.0,1.0,1.0,1.0, 1.0,1.0,1.0,1.0, 1.0,1.0,1.0,0.5, 1.0,1.0,1.0,0.0};
CGFloat locations[] = {0.0, 0.1, 0.2, 0.8, 0.9, 1.0};
CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, 6); //colorSpaceP3
CGPoint center = CGPointMake(100.0, 100.0);
CGContextDrawRadialGradient(context, gradient, center, 0.1, center, radius, 0);
CGGradientRelease(gradient);
CGImageRef imageHole = CGBitmapContextCreateImage(context);
CGImageRef maskHole = CGImageMaskCreate(CGImageGetWidth(imageHole), CGImageGetHeight(imageHole), CGImageGetBitsPerComponent(imageHole), CGImageGetBitsPerPixel(imageHole), CGImageGetBytesPerRow(imageHole), CGImageGetDataProvider(imageHole), NULL, FALSE);
CGImageRelease(imageHole);
CGImageRef image = [UIImage imageNamed:#"prosbo_hires.jpg"].CGImage;
CGImageRef masked = CGImageCreateWithMask(image, maskHole);
CGImageRelease(maskHole);
UIImage *img = [UIImage imageWithCGImage:masked];
CGImageRelease(masked);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
The log says:
: CGImageMaskCreate: invalid mask bits/component: 32.
I don't have much experience with Core Graphics. Can anyone please suggest something here.
Thanks.
The documentation for the bitsPerComponent parameter of CGImageMaskCreate() says:
Image masks must be 1, 2, 4, or 8 bits per component.
You're passing CGImageGetBitsPerComponent(imageHole), which is 32 bits per component. As per both the documentation and the log message, that's not valid.
The implication is that image masks don't support floating point bitmap formats.
It should be possible to create the bitmap context and the mask using 8 bits per component. More or less, just leave out kCGBitmapFloatComponents. I expect that will result in reduced granularity of the opacity of the mask, but won't affect the color range of masked images.
this fixed my issue:
contextRef = CGBitmapContextCreate(
m.data,
m.cols,
m.rows,
8,
m.step[0],
CGColorSpaceCreateDeviceRGB(),
bitmapInfo);
https://developer.apple.com/search/?q=CGColorSpaceCreate
Good day to all.
At the moment I am trying to implement CCLabelTTF subclass with suppport of NSAttributedString to get multi-colored label. And I am hampered by lack of CoreText and CoreGraphics knowledge.
After reading few guides I, created CCTexture2D category to create texture using NSAttributedString object.
Here is my drawing code:
data = calloc(POTHigh, POTWide * 2);
colorSpace = CGColorSpaceCreateDeviceGray();
context = CGBitmapContextCreate(data, POTWide, POTHigh, 8, POTWide, colorSpace, kCGImageAlphaNone);
CGColorSpaceRelease(colorSpace);
if( ! context )
{
free(data);
[self release];
return nil;
}
UIGraphicsPushContext(context);
CGContextTranslateCTM(context, 0.0f, POTHigh);
CGContextScaleCTM(context, 1.0f, -1.0f);
// draw attributed string to context
CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)string);
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, CGRectMake(0.f, 0.f, dimensions.width, dimensions.height));
CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, NULL);
CTFrameDraw(frame, context);
UIGraphicsPopContext();
CFRelease(frame);
CGPathRelease(path);
CFRelease(frameSetter);
And now I have few troubles:
The first one - my texture is shown flipped vertically. I thought, that these lines
CGContextTranslateCTM(context, 0.0f, POTHigh);
CGContextScaleCTM(context, 1.0f, -1.0f);
should prevent this.
The second one, if I create RGB context, I cannot see anything on the screen. I tried to create RGB context with these lines.
colorSpace = CGColorSpaceCreateDeviceRGB();
context = CGBitmapContextCreate(data, POTWide, POTHigh, 8, POTWide * 4, colorSpace, kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Big);
I tried to google, but don't find anything related to my issues =( Any help(links or suggestions) is appreciated.
Couple things to try:
Your data allocation isn't big enough for RGB. Try: data = calloc(POTHigh, POTWide * 4); for RGB color space.
CTFrameDraw draws in relation to GL coords so you don't need to use CGContextScaleCTM(context, 1.0f, -1.0f);
that line was put in the original CCTexture2D creation for a CCLabelTTF because it used NSString's drawInRect: which draws in relation to UIKit coords.
Maybe try other alpha mask flags...? Check out Apple's documentation on Supported Pixel Formats for iOS to see what your options are.
You may want to take a look at ActiveTextView-iOS (https://github.com/storify/ActiveTextView-iOS). It may be of use.
use this to get color texture:
context = CGBitmapContextCreate(data, POTWide, POTHigh, 8, POTWide, colorSpace, kCGImageAlphaPremultipliedLast);
Is there an easy way to get an two-dimensional array or something similar that represents the pixel data of an image?
I have black & white PNG images and I simply want to read the color value at a certain coordinate. For example the color value at 20/100.
This Category on UIImage might be helpful Source
#import <CoreGraphics/CoreGraphics.h>
#import "UIImage+ColorAtPixel.h"
#implementation UIImage (ColorAtPixel)
- (UIColor *)colorAtPixel:(CGPoint)point {
// Cancel if point is outside image coordinates
if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f, self.size.width, self.size.height), point)) {
return nil;
}
// Create a 1x1 pixel byte array and bitmap context to draw the pixel into.
// Reference: http://stackoverflow.com/questions/1042830/retrieving-a-pixel-alpha-value-for-a-uiimage
NSInteger pointX = trunc(point.x);
NSInteger pointY = trunc(point.y);
CGImageRef cgImage = self.CGImage;
NSUInteger width = CGImageGetWidth(cgImage);
NSUInteger height = CGImageGetHeight(cgImage);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
int bytesPerPixel = 4;
int bytesPerRow = bytesPerPixel * 1;
NSUInteger bitsPerComponent = 8;
unsigned char pixelData[4] = { 0, 0, 0, 0 };
CGContextRef context = CGBitmapContextCreate(pixelData,
1,
1,
bitsPerComponent,
bytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextSetBlendMode(context, kCGBlendModeCopy);
// Draw the pixel we are interested in onto the bitmap context
CGContextTranslateCTM(context, -pointX, -pointY);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, (CGFloat)width, (CGFloat)height), cgImage);
CGContextRelease(context);
// Convert color values [0..255] to floats [0.0..1.0]
CGFloat red = (CGFloat)pixelData[0] / 255.0f;
CGFloat green = (CGFloat)pixelData[1] / 255.0f;
CGFloat blue = (CGFloat)pixelData[2] / 255.0f;
CGFloat alpha = (CGFloat)pixelData[3] / 255.0f;
return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}
#end
You could put the png into an image view, and then use this method to get the pixel value from a graphics context that you would draw the the image into.
A class to do it for you, and explained too:
http://www.markj.net/iphone-uiimage-pixel-color/
The direct approach is slightly tedious, but here goes:
Get the CoreGraphics image.
CGImageRef cgImage = image.CGImage;
Get the "data provider", and from that get the data.
NSData * d = [(id)CGDataProviderCopyData(CGImageGetDataProvider(cgImage)) autorelease];
Figure out what format the data is in.
CGImageGetBitmapInfo();
CGImageGetBitsPerComponent();
CGImageGetBitsPerPixel();
CGImageGetBytesPerRow();
figure out the colour space (PNG supports greyscale/RGB/paletted).
CGImageGetColorSpace()
The indirect approach is to draw the image to a context (note that you may need to specify the context's byte order if you want any guarantees) and read the bytes out.
If you only want single pixels, it might be faster to draw the image to a 1x1 context with the right rect
(something like (CGRect){{-x,-y},{imgWidth,imgHeight}}).
This will handle colour-space conversion for you. If you just want a brightness value, use a greyscale context.
I am trying to draw to a bitmap context but coming up empty. I believe I'm creating things properly because I can initialize the context, draw a few things, then create an image from it and draw that image. What I cannot do is, after initialization, trigger further drawing on the context that draws more items on it. I'm not sure if I'm missing some common practice that implies I can only draw it at certain places or that I have to do something else. Here is what I do, below.
I copied the helper function provided by apple with one modification to obtain the color space because it wasn't compiling (this is for iPad, don't know if that matters):
CGContextRef MyCreateBitmapContext (int pixelsWide, int pixelsHigh)
{
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
void * bitmapData;
int bitmapByteCount;
int bitmapBytesPerRow;
bitmapBytesPerRow = (pixelsWide * 4);// 1
bitmapByteCount = (bitmapBytesPerRow * pixelsHigh);
colorSpace = CGColorSpaceCreateDeviceRGB(); //CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);// 2
bitmapData = malloc( bitmapByteCount );// 3
if (bitmapData == NULL)
{
fprintf (stderr, "Memory not allocated!");
return NULL;
}
context = CGBitmapContextCreate (bitmapData,// 4
pixelsWide,
pixelsHigh,
8, // bits per component
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast);
if (context== NULL)
{
free (bitmapData);// 5
fprintf (stderr, "Context not created!");
return NULL;
}
CGColorSpaceRelease( colorSpace );// 6
return context;// 7
}
I initialize it in my init method below with a few sample draws just to be sure it looks right:
mContext = MyCreateBitmapContext (rect.size.width, rect.size.height);
// sample fills
CGContextSetRGBFillColor (mContext, 1, 0, 0, 1);
CGContextFillRect (mContext, CGRectMake (0, 0, 200, 100 ));
CGContextSetRGBFillColor (mContext, 0, 0, 1, .5);
CGContextFillRect (mContext, CGRectMake (0, 0, 100, 200 ));
CGContextSetRGBStrokeColor(mContext, 1.0, 1.0, 1.0, 1.0);
CGContextSetRGBFillColor(mContext, 0.0, 0.0, 1.0, 1.0);
CGContextSetLineWidth(mContext, 5.0);
CGContextAddEllipseInRect(mContext, CGRectMake(0, 0, 60.0, 60.0));
CGContextStrokePath(mContext);
In my drawRect method, I create an image from it to render it. Maybe I should be creating and keeping this image as a member var and updating it everytime I draw something new and not creating the image every frame? (Some advice on this would be nice):
// draw bitmap context
CGImageRef myImage = CGBitmapContextCreateImage (mContext);
CGContextDrawImage(context, rect, myImage);
CGImageRelease(myImage);
Then as a test I try drawing a circle when I touch, but nothing happens, and the touch is definitely triggering:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint location;
for (UITouch* touch in touches)
{
location = [touch locationInView: [touch view]];
}
CGContextSetRGBStrokeColor(mContext, 1.0, 1.0, 1.0, 1.0);
CGContextSetRGBFillColor(mContext, 0.0, 0.0, 1.0, 1.0);
CGContextSetLineWidth(mContext, 2.0);
CGContextAddEllipseInRect(mContext, CGRectMake(location.x, location.y, 60.0, 60.0));
CGContextStrokePath(mContext);
}
Help?
[self setNeedsDisplay]; !!!!
!!!!!!!!!
so it was because drawRect was never being called after init since it didn't know it needed to refresh. My understanding is that I should just call setNeedsDisplay anytime I draw and that seems to work. :)
So I tried to use the Quartz CGImageCreateWithMaskingColors function, but he only problem is that it masks the color range you are selecting.
I want to mask everything but the color range I am selecting. For instance, I want to show all red colors in a picture but remove the other channels (Green and Blue).
I am doing this in Objective-C and I am a noob so please give me examples :)
Any help is greatly appreciated.
use these methods.i found them in one of the SO posts.
-(void)changeColor
{
UIImage *temp23=Image;//Pass your image here
CGImageRef ref1=[self createMask:temp23];
const float colorMasking[6] = {1.0, 3.0, 1.0, 2.0, 2.0, 3.0};
CGImageRef New=CGImageCreateWithMaskingColors(ref1, colorMasking);
UIImage *resultedimage=[UIImage imageWithCGImage:New];
EditImageView.image = resultedimage;
[EditImageView setNeedsDisplay];
}
-(CGImageRef)createMask:(UIImage*)temp
{
CGImageRef ref=temp.CGImage;
int mWidth=CGImageGetWidth(ref);
int mHeight=CGImageGetHeight(ref);
int count=mWidth*mHeight*4;
void *bufferdata=malloc(count);
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGContextRef cgctx = CGBitmapContextCreate (bufferdata,mWidth,mHeight, 8,mWidth*4, colorSpaceRef, kCGImageAlphaPremultipliedFirst);
CGRect rect = {0,0,mWidth,mHeight};
CGContextDrawImage(cgctx, rect, ref);
bufferdata = CGBitmapContextGetData (cgctx);
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, bufferdata, mWidth*mHeight*4, NULL);
CGImageRef savedimageref = CGImageCreate(mWidth,mHeight, 8, 32, mWidth*4, colorSpaceRef, bitmapInfo,provider , NULL, NO, renderingIntent);
CFRelease(colorSpaceRef);
return savedimageref;
}
then call changecolor method on a buttons click event and see the result
I found the answer for my above problem, Follow the above code of Rahul with some changes to set your own color,
-(void)changeColor
{
UIImage *temp23=Image;//Pass your image here
CGImageRef ref1=[self createMask:temp23];
const float colorMasking[6] = {1.0, 3.0, 1.0, 2.0, 2.0, 3.0};
CGImageRef New=CGImageCreateWithMaskingColors(ref1, colorMasking);
UIImage *resultedimage=[UIImage imageWithCGImage:New];
EditImageView.image = resultedimage;
[EditImageView setNeedsDisplay];
}
-(CGImageRef)createMask:(UIImage*)temp
{
CGImageRef ref=temp.CGImage;
int mWidth=CGImageGetWidth(ref);
int mHeight=CGImageGetHeight(ref);
int count=mWidth*mHeight*4;
void *bufferdata=malloc(count);
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGContextRef cgctx = CGBitmapContextCreate (bufferdata,mWidth,mHeight, 8,mWidth*4,colorSpaceRef, kCGImageAlphaPremultipliedLast);
CGRect rect = {0,0,mWidth,mHeight};
CGContextDrawImage(cgctx, rect, ref);
CGContextSaveGState(cgctx);
CGContextSetBlendMode(cgctx, kCGBlendModeColor);
CGContextSetRGBFillColor (cgctx, 1.0, 0.0, 0.0, 1.0);
CGContextFillRect(cgctx, rect);
bufferdata = CGBitmapContextGetData (cgctx);
const float colorMasking[6] = {1.0, 3.0, 1.0, 2.0, 2.0, 3.0};
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, bufferdata, mWidth*mHeight*4, NULL);
CGImageRef savedimageref = CGImageCreate(mWidth,mHeight, 8, 32, mWidth*4, colorSpaceRef, bitmapInfo,provider , NULL, NO, renderingIntent);
CFRelease(colorSpaceRef);
return savedimageref;
}
Hmmm...
I may be missing something, but I don't believe that the provided answers apply to the question. The second response gets closer to the mark, but it contains spurious code that has little to do with the solution.
The createMask method makes a copy of the original image assuming alpha in LSB position. The changeColor performs a masking call that isn't going to do much to an RGB image -- basically only black is going to be masked (i.e, RGB triplets in the range/combinations of (1,1,2) to (3,2,1)).
I am guessing that the red shift that is being observed is due to the parameter
kCGImageAlphaPremultipliedFirst
in the line
CGContextRef cgctx = CGBitmapContextCreate (bufferdata,mWidth,mHeight, 8,mWidth*4, colorSpaceRef, kCGImageAlphaPremultipliedFirst);
due to improper treatment of the alpha channel. If in the changeColor method you modify the block
CGImageRef ref1=[self createMask:temp23];
const float colorMasking[6] = {1.0, 3.0, 1.0, 2.0, 2.0, 3.0};
CGImageRef New=CGImageCreateWithMaskingColors(ref1, colorMasking);
UIImage *resultedimage=[UIImage imageWithCGImage:New];
EditImageView.image = resultedimage;
to be
CGImageRef ref1=[self createMask:temp23];
UIImage *resultedimage=[UIImage imageWithCGImage:ref];
EditImageView.image = resultedimage;
you'll see no difference in the display. Changing the CGBitmapInfo constant to kCGImageAlphaPremultipliedLast should display the image correctly using either of the above code blocks.
The next response gets a bit closer to what the OP asks for, but its in terms of visual effect, not actual data. Here the pertinent code in createMask is
CGContextRef cgctx = CGBitmapContextCreate (bufferdata,mWidth,mHeight, 8,mWidth*4,colorSpaceRef, kCGImageAlphaPremultipliedLast);
which displays the image correctly, followed by
CGContextSetBlendMode(cgctx, kCGBlendModeColor);
CGContextSetRGBFillColor (cgctx, 1.0, 0.0, 0.0, 1.0);
CGContextFillRect(cgctx, rect);
and then the logic for constructing the image. The blend logic overlays a red tint on the original image, achieving a similar effect as the misplaced alpha channel in the original response. This still really is not what the OP asks for, which is to mask one or more channels, not blend colors.
This really amounts to setting the channel values for the colors that are not desired to zero. Here's an example for returning just the red channel as the OP requests; the assumption is that the format of the pixel is ABGR:
- (CGImageRef) redChannel:(CGImageRef)image
{
CGDataProviderRef provider = CGImageGetDataProvider(image);
NSMutableData* data = (id)CGDataProviderCopyData(provider);
int width = CGImageGetWidth(image);
int height = CGImageGetHeight(image);
[data autorelease];
// get a mutable reference to the image data
uint32_t* dwords = [data mutableBytes];
for (size_t idx = 0; idx < width*height; idx++) {
uint32_t* pixel = &dwords[idx];
// perform a logical AND of the pixel with a mask that zeroes out green and blue pixels
*pixel &= 0x000000ff;
}
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
// now create a new image using the masked original data
CGDataProviderRef iprovider = CGDataProviderCreateWithData(NULL, dwords, width*height*4, NULL);
CGImageRef savedimageref = CGImageCreate(width, height, 8, 32, width*4, colorSpaceRef, bitmapInfo, iprovider, NULL, NO, renderingIntent);
CGColorSpaceRelease(colorSpaceRef);
CGDataProviderRelease(iprovider);
return savedimageref;
}
A good summary of bitwise operations can be found here.
As is pointed out here, you may need to change the structure of the mask depending on the LSB/MSB ordering of the bits in the pixel. This example assumes 32 bit pixels from a standard iPhone PNG.