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README.md

SYImageColorTools

It's always a hassle to get pixel information of an UIImage. Let's remedy that!

Use pod SYImageColorTools/GPUImage to enjoy the same methods with data coming from GPUImageFramebuffer objects.

###SYImageColorGetter

Pretty straightforward class, to access pixels of an image. Its only goal is to keep the image data in memory so that if you have multiple pixels to get you reduce the buffer allocation overhead.

@interface SYImageColorGetter : NSObject

- (instancetype)initWithImage:(UIImage *)image;

- (UIColor *)getColorAtPoint:(CGPoint)point;
- (CGFloat)getRedAtPoint:(CGPoint)point;
- (CGFloat)getGreenAtPoint:(CGPoint)point;
- (CGFloat)getBlueAtPoint:(CGPoint)point;
- (CGFloat)getAlphaAtPoint:(CGPoint)point;

@end

###SYImageColorTools

Allows getting pixels value from a buffer, created from an OpenGL texture (when using GPUImage for instance) or an UIImage

It defines multiple types:

  • SYPixel: struct containing r, g, b and a data for a pixel
  • SYImageInfo: struct containing the required information about the buffer to understand it; used by SYImageGetPixelValue and SYImageDetermineEdgeInsetsToTrimTransparentPixels

Here is the header:

typedef struct {
    CGFloat r;
    CGFloat g;
    CGFloat b;
    CGFloat a;
} SYPixel;

typedef struct {
    NSUInteger width;
    NSUInteger height;
    NSUInteger bytesPerRow;
    BOOL alphaOnly;
    BOOL alphaFirst;
    BOOL alphaPremultiplied;
    BOOL bigEndian;
} SYImageInfo;

// Create a basic SYImageInfo struct for a GPUImage based buffer 
SYImageInfo SYImageInfoCreateForOpenGLTexture(NSUInteger w, NSUInteger h);

// Get pixel value in a given buffer, understandable with the SYImageInfo parameter
SYPixel SYImageGetPixelValue(const uint8_t *data, SYImageInfo info, NSUInteger x, NSUInteger y, BOOL onlyAlpha);

// Returns the number of lines and columns to remove from the image on each side to remove all completely transparent lines
UIEdgeInsets SYImageDetermineEdgeInsetsToTrimTransparentPixels(const uint8_t *data, SYImageInfo imageInfo, CGFloat maxAlpha);

###UIColor+SYImageColorTools

Simple category to create a UIColor from a SYPixel struct

@interface UIColor (SYImageColorTools)

+ (UIColor *)colorWithSYPixel:(SYPixel)pixel;

@end

###UIImage+SYImageColorTools

Category bringing higher level methods for SYImageColorTools functions

@interface UIImage (SYImageColorTools)

- (SYImageInfo)imageInfo;
- (UIColor *)colorAtPoint:(CGPoint)pixelPoint;
- (UIImage *)imageByTrimmingTransparentPixels;

@end

#SYImageColorTools/GPUImage

Additions to GPUImage to work with SYImageColorTools allowing you to read data from then OpenGL buffer of a filter.

###GPUImageFramebuffer+SYImageColorTools

Helps using SYImageColorTools with GPUImageFramebuffer by obtaining a buffer and the appriopriate image info.

typedef void(^SYImageBytesBlock)(GLubyte *bytes, SYImageInfo info);

@interface GPUImageFramebuffer (SYImageColorTools)

- (void)getBytes:(SYImageBytesBlock)block;

@end

###SYGPUImageFilterWhiteSpaceTrimmer

GPUImage filter that will compute the crop region each time it has the chance, and give you access to those values. The computation is done on the CPU since I wouldn't know how to it and the crop on the GPU. The crop isn't done at all, you will need to use the lastComputedCropRegion property to crop it yourself. Sorry ¯\(ツ)

@interface SYGPUImageFilterWhiteSpaceTrimmer : GPUImageFilter

@property (nonatomic, assign) CGFloat maxAlpha;
@property (nonatomic, assign) CGRect lastComputedCropRegion;
@property (nonatomic, assign) CGRect lastComputedCropRegionNormalized;
@property (nonatomic, assign) BOOL cropRegionDefined;

@end

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It's always a hassle to get pixel information of an UIImage. Let's remedy that!

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