UIImage gradient from two Colors

Gradient images look like very attractive, isn't it?
With this powerful Objective-C method creating an UIImage gradient image is too easy.
You need:
- http://objective-c-functions.blogspot.com/2013/06/helpful-color-struct-rgb-hsv.html
- http://objective-c-functions.blogspot.com/2013/06/get-rgba-components-of-uicolor.html


/** Returns a gradient image.

 @param startColor Color to start from.
 @param endColor Color to end to.
 @param size Size of the result image.
 @return Returns a new UIImage which is the result of gradient effect from two colors.

 */
+ (UIImage *)imageGradientWithStartColor:(UIColor *)startColor endColor:(UIColor *)endColor size:(CGSize)size {

    // Allocate color space.
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    // Allocate bitmap context.
    CGContextRef bitmapCotext = CGBitmapContextCreate(NULL, size.width, size.height, 8, 4 * size.width, colorSpace, kCGImageAlphaPremultipliedFirst);
    // Create the gradient.
    CGFloat locations[2] = { 0.0f, 1.0f };
    COLOR_RGBA startRgba    = [LMFunctions rgbaFromUIColor:startColor];
    COLOR_RGBA endRgba        = [LMFunctions rgbaFromUIColor:endColor];
    CGFloat components[8] = {
        startRgba.r, startRgba.g, startRgba.b, 1.0f,    // Start color.
        endRgba.r, endRgba.g, endRgba.b, 1.0f };        // End color.
    CGGradientRef myGradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, 2);
    // Draw gradient here.
    CGContextDrawLinearGradient(bitmapCotext, myGradient, CGPointMake(0, 0), CGPointMake(size.width, size.height), kCGGradientDrawsAfterEndLocation);
    // Create a CGImage from context.
    CGImageRef cgImage = CGBitmapContextCreateImage(bitmapCotext);
    // Create a UIImage from CGImage.
    UIImage *uiImage = [UIImage imageWithCGImage:cgImage];

    // Release resources.
    CGGradientRelease(myGradient);
    CGImageRelease(cgImage);
    CGContextRelease(bitmapCotext);
    CGColorSpaceRelease(colorSpace);

    return uiImage;
}


Download the ready-for-use source file (.m) of UIImage gradient from two Colors

Flip UIButton title and image

Let's say we have a UIButton which can assume two state. With this convenient function we can do a flip animation between two images and two titles.


/** Flip animation for title and image of a button.

 The button action does not change. This function changes only the title and the image associated to the button.

 @param baseBtn Shared button.
 @param baseView A container View. It only serves for animation effect.
 @param title1 String of the first title.
 @param img1 First image.
 @param title2 String of the second title.
 @param img2 Second image.
 @return Returns true on success, false otherwise.

 */
+ (BOOL)flipButton:(UIButton *)baseBtn ofView:(UIView *)baseView
        withTitle1:(NSString *)title1 img1:(UIImage *)img1
        withTitle2:(NSString *)title2 img2:(UIImage *)img2 {

    NSString *newTitle;
    UIImage *newImage;
    UIViewAnimationTransition flip;

    if ([baseBtn.currentTitle isEqualToString:title1]) {
        newTitle = title2;
        newImage = img2;
        flip = UIViewAnimationTransitionFlipFromRight;
    } else if ([baseBtn.currentTitle isEqualToString:title2]) {
        newTitle = title1;
        newImage = img1;
        flip = UIViewAnimationTransitionFlipFromLeft;
    } else {
        LogError(@"No button found with title: '%@' or '%@'", title1, title2);
        return NO;
    }

    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration: 0.50f];
    [UIView setAnimationTransition:flip forView:baseView cache:YES];

    [baseBtn setTitle:newTitle forState:UIControlStateNormal];
    [baseBtn setImage:newImage forState:UIControlStateNormal];

    [UIView commitAnimations];

    return YES;
}


Download the ready-for-use source file (.m) of Flip UIButton title and image

Content mode for scaled, resized or cropped image

How to scale or resize or crop a UIImage image in order to fit in a box? This is my implementation.


/** Returns the appropriate content mode for correctly viewing an image inside a container.

 Default behaviour is: if the image is larger (in width) than container then it'll be resized; if it's longer (in height) it'll be cropped at the bottom.

 @param imageSize The size of the image.
 @param limits The bounds of the container.
 @return Returns the right UIViewContentMode value.

 */
+ (UIViewContentMode)contentModeForImageOfSize:(CGSize)imageSize insideBounds:(CGSize)limits {

    if (imageSize.width > limits.width) {
        return UIViewContentModeScaleAspectFit;
    } else {
        return UIViewContentModeCenter;
    }
}


Download the ready-for-use source file (.m) of Content mode for scaled, resized or cropped image

ARGB raw data from bitmap

This is not a simple nor straightforward method, because it involves CGImageRef, CGContextRef and raw image data manipulation.
But what it's actually doing is very clear: it takes an image and create its ARGB rappresentation.



/** Create an ARGB Bitmap from image.

 @param image CGImageRef of original image.
 @return Returns the CGContextRef of a Bitmap representing the image.

 */
+ (CGContextRef)createARGBBitmapContextFromImage:(CGImageRef)image {

    CGContextRef context = NULL;
    CGColorSpaceRef colorSpace;
    void *bitmapData;
    int bitmapByteCount;
    int bitmapBytesPerRow;

    // Get image width and height. We'll use the entire image.
    size_t pixelsWide = 1;
    size_t pixelsHigh = 1;

    // Declare the number of bytes per row. Each pixel in the bitmap is represented by 4 bytes; 8 bits each of red, green, blue, and alpha.
    bitmapBytesPerRow    = (pixelsWide * 4);
    bitmapByteCount        = (bitmapBytesPerRow * pixelsHigh);

    // Use the generic RGB color space.
    colorSpace = CGColorSpaceCreateDeviceRGB();
    if (colorSpace == NULL) {
        fprintf(stderr, "Error allocating color space");
        return NULL;
    }

    // Allocate memory for image data. This is the destination in memory where any drawing to the bitmap context will be rendered.
    bitmapData = malloc(bitmapByteCount);
    if (bitmapData == NULL) {
        fprintf (stderr, "Memory not allocated!");
        CGColorSpaceRelease(colorSpace);
        return NULL;
    }

    // Create the bitmap context. We want pre-multiplied ARGB, 8-bits per component.
    // Regardless of what the source image format is (CMYK, Grayscale, ...) it will be converted over to the format specified here by CGBitmapContextCreate.
    context = CGBitmapContextCreate (bitmapData,
                                     pixelsWide,
                                     pixelsHigh,
                                     8, // Bits per component.
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     kCGImageAlphaPremultipliedFirst);
    if (context == NULL) {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
    }

    // Release colorspace before returning.
    CGColorSpaceRelease(colorSpace);

    return context;
}



Download the ready-for-use source file (.m) of ARGB raw data from bitmap