I got a UIImage from UIImagePickerController, and using the code from this site to resize the image
- (UIImage *)resizedImage:(CGSize)newSize
transform:(CGAffineTransform)transform
drawTransposed:(BOOL)transpose
interpolationQuality:(CGInterpolationQuality)quality {
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
CGImageRef imageRef = self.CGImage;
// Build a context that's the same dimensions as the new size
CGContextRef bitmap = CGBitmapContextCreate(NULL,
newRect.size.width,
newRect.size.height,
CGImageGetBitsPerComponent(imageRef),
0,
CGImageGetColorSpace(imageRef),
CGImageGetBitmapInfo(imageRef));
// Rotate and/or flip the image if required by its orientation
CGContextConcatCTM(bitmap, transform);
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(bitmap, quality);
// Draw into the context; this scales the image
CGContextDrawImage(bitmap, transpose ? transposedRect : newRect, imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
// Clean up
CGContextRelease(bitmap);
CGImageRelease(newImageRef);
return newImage;
}
UIImagePNGRepresentation() failed to return NSData on re-sized image, but UIImageJPEGRepresentation() succeed.
How do we know if a UIImage is presentable in PNG or JPEG? What missed in the above code that make the resized image can not be represented in PNG?
According to apple document: "This function may return nil if the image has no data or if the underlying CGImageRef contains data in an unsupported bitmap format."
What bitmap format supported by PNG presentation? How to make an UIImage PNG-supported format?
That was a mistake that in another part of the code the image was rescaled with the following
CGContextRef context = CGBitmapContextCreate(NULL,
size.width,
size.height,
8,
0,
CGImageGetColorSpace(source),
kCGImageAlphaNoneSkipFirst);
Changing kCGImageAlphaNoneSkipFirst to CGImageGetBitmapInfo(source) fixed the problem
go to following link...
How to check if downloaded PNG image is corrupt?
it may help you...
Let me know it is working or not...
Happy Coding!!!!
Related
I have a resource (.png file) that show a picture frame (border).
This .png file is size 100x100px, and the border width is 10px.
My Question:
How can I create another UIImage from this image, with a different size, without ruin the border's width?
The Problem:
When I try to draw the new image from the original image with CGContextDrawImage I get a new image with the new size, but my border proportion is ruin.
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newWidth, newHeight));
CGImageRef imageRef = //... the image
// Build a context that's the same dimensions as the new size
CGContextRef bitmap = CGBitmapContextCreate(NULL,
newRect.size.width,
newRect.size.height,
CGImageGetBitsPerComponent(imageRef),
0,
CGImageGetColorSpace(imageRef),
CGImageGetBitmapInfo(imageRef));
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(bitmap, kCGInterpolationHigh);
// Draw into the context; this scales the image
CGContextDrawImage(bitmap, newRect, imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
// Clean up
CGContextRelease(bitmap);
CGImageRelease(newImageRef);
For example, when I tried to create an image size 800x100p, I get an image with very thin top and bottom border.
What I need is that the border will stay the same width
*note
Using resizableImageWithCapInsets: wont help me, because I need a new image with the new size to save on the disc.
You can use resizableImageWithCapInsets:
UIImage *img = [UIImage imageNamed:#"myResource"];
img = [img resizableImageWithCapInsets:UIEdgeInsetsMake(10,10,10,10)];
I've never used this approach with CGContextDrawImage, but it should work.
I was searching on the google if I get something for add effect to the Image like Black & White, Sepia, grayScale etc. I found a useful link for converting Image in Sepia but there is nothing for converting it in B&W or Grayscale.
Here is the link http://groups.google.com/group/iphonesdkdevelopment/browse_thread/thread/b987b02deec08b9f
After going through the code I come to know that we need to change RBG for that but How to get RBG for B&W and grayScale. What will be the RBG ratio for these kind of effects.
Any help will be appreciate.
Thanks In Advance
You can get a B&W Image by
-(UIImage *)convertOriginalImageToBWImage:(UIImage *)originalImage
{
UIImage *newImage;
CGColorSpaceRef colorSapce = CGColorSpaceCreateDeviceGray();
CGContextRef context = CGBitmapContextCreate(nil, originalImage.size.width * originalImage.scale, originalImage.size.height * originalImage.scale, 8, originalImage.size.width * originalImage.scale, colorSapce, kCGImageAlphaNone);
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGContextSetShouldAntialias(context, NO);
CGContextDrawImage(context, CGRectMake(0, 0, originalImage.size.width, originalImage.size.height), [originalImage CGImage]);
CGImageRef bwImage = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSapce);
UIImage *resultImage = [UIImage imageWithCGImage:bwImage];
CGImageRelease(bwImage);
UIGraphicsBeginImageContextWithOptions(originalImage.size, NO, originalImage.scale);
[resultImage drawInRect:CGRectMake(0.0, 0.0, originalImage.size.width, originalImage.size.height)];
newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
You need to do that is same way as given in the link(google groups).
Also, you can find the logic in this link to convert them into grayScale.
Hope this helps you.
Wondering if there is a way to isolate a single color in an image either using masks or perhaps even a custom color space. I'm ultimately looking for a fast way to isolate 14 colors out of an image - figured if there was a masking method it might may be faster than walking through the pixels.
Any help is appreciated!
You could use a custom color space (documentation here) and then substitute it for "CGColorSpaceCreateDeviceGray()" in the following code:
- (UIImage *)convertImageToGrayScale:(UIImage *)image
{
// Create image rectangle with current image width/height
CGRect imageRect = CGRectMake(0, 0, image.size.width, image.size.height);
// Grayscale color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); // <- SUBSTITUTE HERE
// Create bitmap content with current image size and grayscale colorspace
CGContextRef context = CGBitmapContextCreate(nil, image.size.width, image.size.height, 8, 0, colorSpace, kCGImageAlphaNone);
// Draw image into current context, with specified rectangle
// using previously defined context (with grayscale colorspace)
CGContextDrawImage(context, imageRect, [image CGImage]);
// Create bitmap image info from pixel data in current context
CGImageRef imageRef = CGBitmapContextCreateImage(context);
// Create a new UIImage object
UIImage *newImage = [UIImage imageWithCGImage:imageRef];
// Release colorspace, context and bitmap information
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);
CFRelease(imageRef);
// Return the new grayscale image
return newImage;
}
This code is from this blog which is worth a look at for removing colors from images.
How can I load an image from photo library and show it in imageView?
How can I change image to black and white?
If you want to load an image from photo library, you have to use UIImagePickerController class. Refer this Link
To convert image form UIImagePickerController to black and white you can use this code:
UIImage *originalImage = [info objectForKey:UIImagePickerControllerOriginalImage]; // this image we get from UIImagePickerController
CGColorSpaceRef colorSapce = CGColorSpaceCreateDeviceGray();
CGContextRef context = CGBitmapContextCreate(nil, originalImage.size.width, originalImage.size.height, 8, originalImage.size.width, colorSapce, kCGImageAlphaNone);
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGContextSetShouldAntialias(context, NO);
CGContextDrawImage(context, CGRectMake(0, 0, originalImage.size.width, originalImage.size.height), [originalImage CGImage]);
CGImageRef bwImage = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSapce);
UIImage *resultImage = [UIImage imageWithCGImage:bwImage]; // This is result B/W image.
CGImageRelease(bwImage);
I'm using the following code to crop and create a new UIImage out of a bigger one. I've isolated the issue to be with the function CGImageCreateWithImageInRect() which seem to not set some CGImage property the way I want. :-) The problem is that a call to function UIImagePNGRepresentation() fails returning a nil.
CGImageRef origRef = [stillView.image CGImage];
CGImageRef cgCrop = CGImageCreateWithImageInRect( origRef, theRect);
UIImage *imgCrop = [UIImage imageWithCGImage:cgCrop];
...
NSData *data = UIImagePNGRepresentation ( imgCrop);
-- libpng error: No IDATs written into file
Any idea what might wrong or alternative for cropping a rect out of UIImage?
I had the same problem, but only when testing compatibility on iOS 3.2. On 4.2 it works fine.
In the end I found this http://www.hive05.com/2008/11/crop-an-image-using-the-iphone-sdk/ which works on both, albeit a little more verbose!
I converted this into a category on UIImage:
UIImage+Crop.h
#interface UIImage (Crop)
- (UIImage*) imageByCroppingToRect:(CGRect)rect;
#end
UIImage+Crop.m
#implementation UIImage (Crop)
- (UIImage*) imageByCroppingToRect:(CGRect)rect
{
//create a context to do our clipping in
UIGraphicsBeginImageContext(rect.size);
CGContextRef currentContext = UIGraphicsGetCurrentContext();
//create a rect with the size we want to crop the image to
//the X and Y here are zero so we start at the beginning of our
//newly created context
CGRect clippedRect = CGRectMake(0, 0, rect.size.width, rect.size.height);
CGContextClipToRect( currentContext, clippedRect);
//create a rect equivalent to the full size of the image
//offset the rect by the X and Y we want to start the crop
//from in order to cut off anything before them
CGRect drawRect = CGRectMake(rect.origin.x * -1,
rect.origin.y * -1,
self.size.width,
self.size.height);
//draw the image to our clipped context using our offset rect
CGContextTranslateCTM(currentContext, 0.0, rect.size.height);
CGContextScaleCTM(currentContext, 1.0, -1.0);
CGContextDrawImage(currentContext, drawRect, self.CGImage);
//pull the image from our cropped context
UIImage *cropped = UIGraphicsGetImageFromCurrentImageContext();
//pop the context to get back to the default
UIGraphicsEndImageContext();
//Note: this is autoreleased
return cropped;
}
#end
In a PNG there are various chunks present, some containing palette info, some actual image data and some other information, it's a very interesting standard. The IDAT chunk is the bit that actually contains the image data. If there's no "IDAT written into file" then libpng has had some issue creating a PNG from the input data.
I don't know exactly what your stillView.image is, but what happens when you pass your code a CGImageRef that is certainly valid? What are the actual values in theRect? If your theRect is beyond the bounds of the image then the cgCrop you're trying to use to make the UIImage could easily be nil - or not nil, but containing no image or an image with width and height 0, giving libpng nothing to work with.
It seems the solution you are trying should work, but I recommend to use this:
CGImageRef image = [stillView.image CGImage];
CGRect cropZone;
size_t cWitdh = cropZone.size.width;
size_t cHeight = cropZone.size.height;
size_t bitsPerComponent = CGImageGetBitsPerComponent(image);
size_t bytesPerRow = CGImageGetBytesPerRow(image) / CGImageGetWidth(image) * cWidth;
//Now we build a Context with those dimensions.
CGContextRef context = CGBitmapContextCreate(nil, cWitdh, cHeight, bitsPerComponent, bytesPerRow, CGColorSpaceCreateDeviceRGB(), CGImageGetBitmapInfo(image));
CGContextDrawImage(context, cropZone, image);
CGImageRef result = CGBitmapContextCreateImage(context);
UIImage * cropUIImage = [[UIImage alloc] initWithCGImage:tmp];
CGContextRelease(context);
CGImageRelease(mergeResult);
NSData * imgData = UIImagePNGRepresentation ( cropUIImage);
UIImage *croppedImage = [self imageByCropping:yourImageView.image toRect:heredefineyourRect];
CGSize size = CGSizeMake(croppedImage.size.height, croppedImage.size.width);
UIGraphicsBeginImageContext(size);
CGPoint pointImg1 = CGPointMake(0,0);
[croppedImage drawAtPoint:pointImg1 ];
[[UIImage imageNamed:yourImagenameDefine] drawInRect:CGRectMake(0,532, 150,80) ];//here define your Reactangle
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
croppedImage = result;
yourCropImageView.image=croppedImage;
[yourCropImageView.image retain];