Help!
I've searched extensively and I haven't found a solution to this "simple" problem. What I am attempting to do is replace white pixels with alpha. It looks like CGImageCreateWithMaskingColors should give me what I want, unfortunately it returns nil in every case. Here's my code, what am I doing wrong?
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, size.width, size.height, 8, 4 * size.width, colorSpace, kCGImageAlphaPremultipliedFirst);
//draw a black background
CGContextSetRGBFillColor(context,0,0, 0, 1);
CGContextFillRect(context, CGRectMake(0, 0, size.width, size.height));
char* text2 = (char *)[text cStringUsingEncoding:NSASCIIStringEncoding];
CGContextSelectFont(context, "Helvetica Bold", kFontSize, kCGEncodingMacRoman);
CGContextSetTextDrawingMode(context, kCGTextFill);
//draw text with the "alpha" color white)
CGContextSetRGBFillColor(context, 1, 1, 1, 1);
float textLength = 20;
CGContextShowTextAtPoint(context, (size.width/2)-(textLength/2), ((size.height/2)-(kFontSize/2))+5, text2, strlen(text2));
//create the black/white image
CGImageRef alphaMask = CGBitmapContextCreateImage(context);
const float colorMasking[6] = {0xEE, 0xFF, 0xEE, 0xFF, 0xEE, 0xFF};
CGImageRef imageMasked = CGImageCreateWithMaskingColors(alphaMask, colorMasking);
imageMasked is nil no matter what I try. I would appreciate any help you can provide, thanks!
Related
This function return a black image. I use the Sparrow Library.
This is my code :
-(UIImage *) saveRectangle:(SPRectangle*)rectangle
{
int numberOfComponents = 8;
int width = rectangle.width;
int height = rectangle.height;
NSInteger bufferLenght = width * height * numberOfComponents;
NSMutableData * buffer= [NSMutableData dataWithLength:bufferLenght];
glPixelStorei(GL_PACK_ALIGNMENT, 4); // force 4 byte alignment
glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, [buffer mutableBytes]);
CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, [buffer mutableBytes], bufferLenght, NULL);
CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, CGColorSpaceCreateDeviceRGB(), kCGBitmapByteOrderDefault, ref, NULL, true, kCGRenderingIntentDefault);
uint32_t* pixels = (uint32_t *)malloc(bufferLenght);
CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width*4, CGImageGetColorSpace(iref), kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Big);
CGContextTranslateCTM(context, 0.0, height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(0.0, 0.0, width, height), iref);
CGImageRef outputRef = CGBitmapContextCreateImage(context);
free(pixels);
return [UIImage imageWithCGImage:outputRef];
}
The code you show has very little Sparrow code to it (other than the SPRectangle which is very akin to a CGRect). Sounds like you're trying to save a capture of a rectangular area of a Sparrow scene. Sparrow intends to abstract you from the OpenGL implementation details. Are you sure it wouldn't be easier to just use an SPRenderTexture? http://doc.sparrow-framework.org/core/Classes/SPRenderTexture.html
Also be sure you want to return an UIImage and not a SPImage. Hope it helps.
I am Rotating the image by using this code
- (CGImageRef)CGImageRotatedByAngle:(CGImageRef)imgRef angle:(CGFloat)angle
{
CGFloat angleInRadians = angle * (M_PI / 360);
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGRect imgRect = CGRectMake(0, 0, width, height);
CGAffineTransform transform = CGAffineTransformMakeRotation(angleInRadians);
CGRect rotatedRect = CGRectApplyAffineTransform(imgRect, transform);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bmContext = CGBitmapContextCreate(NULL,
rotatedRect.size.width,
rotatedRect.size.height,
8,
0,
colorSpace,
kCGImageAlphaPremultipliedFirst);
CGContextSetAllowsAntialiasing(bmContext, YES);
CGContextSetShouldAntialias(bmContext, YES);
CGContextSetInterpolationQuality(bmContext, kCGInterpolationHigh);
CGColorSpaceRelease(colorSpace);
CGContextTranslateCTM(bmContext,
+(rotatedRect.size.width/2),
+(rotatedRect.size.height/2));
CGContextRotateCTM(bmContext, angleInRadians);
CGContextTranslateCTM(bmContext,
-(rotatedRect.size.width/2),
-(rotatedRect.size.height/2));
CGContextDrawImage(bmContext, CGRectMake(0, 0,
rotatedRect.size.width,
rotatedRect.size.height),
imgRef);
CGImageRef rotatedImage = CGBitmapContextCreateImage(bmContext);
CFRelease(bmContext);
// [(id)rotatedImage autorelease];
return rotatedImage;
}
By this i am having the resultant image like this..
those white spaces should not be there and it should follow the same pattern of that size with out that white spaces around..the rotated image....
Please help..Thanks in advance
I know the documentation says that CGBitMapContextCreate doesn't support indexed color spaces. That's troubling for me. I have a bunch of 256bit PNG files that I need to display, which are all indexed color spaces:
<CGColorSpace 0x101301000> (kCGColorSpaceICCBased; kCGColorSpaceModelRGB; sRGB IEC61966-2.1)
How can I convert the CGImageRef to a supported colorspace so that I can make this work?
Here's my method, which is having trouble:
- (BOOL) renderToBuffer:(void*)baseAddress withBytesPerRow:(NSUInteger)rowBytes pixelFormat:(NSString*)format forBounds:(NSRect)bounds
{
CGContextRef context = CGBitmapContextCreate(baseAddress, bounds.size.width, bounds.size.height,
8, rowBytes, CGImageGetColorSpace(img),
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGImageRef imageRef = CGImageCreateWithImageInRect(img, bounds);
CGContextDrawImage(context, CGRectMake(0, 0, bounds.size.width, bounds.size.height), imageRef);
CGImageRelease(imageRef);
CGContextRelease(context);
return YES;
}
CGColorSpaceRef colorspace = CGImageGetColorSpace(image);
CGContextRef context = CGBitmapContextCreate(NULL, width, height,
CGImageGetBitsPerComponent(image),
CGImageGetBytesPerRow(image),
colorspace,
CGImageGetAlphaInfo(image));
CGColorSpaceRelease(colorspace);
if(context == NULL)
return nil;
CGContextDrawImage(context, CGRectMake(0, 0, width, height), image);
CGImageRef imgRef = CGBitmapContextCreateImage(context);
CGContextRelease(context);
This is my full code....
CGBitmapContextCreate returns an object through the COPY operation. You need to release it too.
you must call CGContextRelease on context.
I'm having a UIView that renders some text using CoreText,everything works fine,
except for the fact that the entire view has black background color.
I've tried the most basic solutions like
[self setBackgroundColor:[UIColor clearColor]];
or
CGFloat components[] = {0.f, 0.f, 0.f, 0.f };
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGColorRef transparent = CGColorCreate(rgbColorSpace, components);
CGContextSetFillColorWithColor(context, transparent);
CFRelease(transparent);
but this didn't help at all.
I'm just pounding my head on this issue, because I can't quite understand
how does really core text works and how is this pure-C layer related
with all the other objective-c stuff.
And this doesn't help very much in solving this problem,
so I'm asking you folks, if could you provide me a solution and (most important)
an explanation about it.
FIY I'm posting also the code of the CoreText view.
it's all based on 2 functions: parseText which builds up the CFAttributedString and the
drawRect that takes care of the drawing part.
-(void) parseText {
NSLog(#"rendering this text: %#", symbolHTML);
attrString = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
CFAttributedStringReplaceString (attrString, CFRangeMake(0, 0), (CFStringRef)symbolHTML);
CFStringRef fontName = (CFStringRef)#"MetaSerif-Book-Accent";
CTFontRef myFont = CTFontCreateWithName((CFStringRef)fontName, 18.f, NULL);
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat components[] = { 1.0, 0.3f, 0.3f, 1.f };
CGColorRef redd = CGColorCreate(rgbColorSpace, components);
CFAttributedStringSetAttribute(attrString, CFRangeMake(0,0),
kCTForegroundColorAttributeName, redd);
CFRelease(redd);
CFAttributedStringSetAttribute(attrString, CFRangeMake(0, CFStringGetLength((CFStringRef)symbolHTML)), kCTFontAttributeName, myFont);
CTTextAlignment alignment = kCTLeftTextAlignment;
CTParagraphStyleSetting settings[] = {
{kCTParagraphStyleSpecifierAlignment, sizeof(alignment), &alignment}
};
CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(settings, sizeof(settings) / sizeof(settings[0]));
CFAttributedStringSetAttribute(attrString, CFRangeMake(0, CFStringGetLength((CFStringRef)attrString)), kCTParagraphStyleAttributeName, paragraphStyle);
[self calculateHeight];
}
and this is the DrawRect function:
- (void)drawRect:(CGRect)rect {
/* get the context */
CGContextRef context = UIGraphicsGetCurrentContext();
/* flip the coordinate system */
float viewHeight = self.bounds.size.height;
CGContextTranslateCTM(context, 0, viewHeight);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetTextMatrix(context, CGAffineTransformMakeScale(1.0, 1.0));
/* generate the path for the text */
CGMutablePathRef path = CGPathCreateMutable();
CGRect bounds = CGRectMake(0, 0, self.bounds.size.width-20.0, self.bounds.size.height);
CGPathAddRect(path, NULL, bounds);
/* draw the text */
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attrString);
CTFrameRef frame = CTFramesetterCreateFrame(framesetter,
CFRangeMake(0, 0), path, NULL);
CFRelease(framesetter);
CFRelease(path);
CTFrameDraw(frame, context);
CGFloat components[] = {0.f, 0.f, 0.f, 0.f };
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGColorRef transparent = CGColorCreate(rgbColorSpace, components);
CGContextSetFillColorWithColor(context, transparent);
CFRelease(transparent);
}
I hope that everything is clear, but if something looks
confusing, just ask and I'll be glad to explain myself better.
thank you in advance for this hardcore issue :)
k
Here's a question. Did you remember to set view.opaque = NO? Because if not you'll get that black background regardless of what else you do.