对openGL来说是全新的。我有这个代码，它使用OpenGl显示我的图像。
#import "ImageView.h"
#import <OpenGL/OpenGL.h>
#import <OpenGL/gl.h>
@interface ImageView ()
@property (nonatomic, strong) CIContext *context;
@property (nonatomic, strong) NSDictionary *contextOptions;
- (BOOL)displaysWhenScreenProfileChanges;
- (void)viewWillMoveToWindow:(NSWindow*)newWindow;
- (void)displayProfileChanged:(NSNotification*)notification;
@end
@implementation ImageView
{
NSRect _lastBounds;
CGLContextObj _cglContext;
NSOpenGLPixelFormat *pixelFormat;
CGDirectDisplayID _directDisplayID;
}
+ (NSOpenGLPixelFormat *)defaultPixelFormat
{
static NSOpenGLPixelFormat *pf;
if (pf == nil)
{
/*
Making sure the context's pixel format doesn't have a recovery renderer is important - otherwise CoreImage may not be able to create deeper context's that share textures with this one.
*/
static const NSOpenGLPixelFormatAttribute attr[] = {
NSOpenGLPFAAccelerated,
NSOpenGLPFANoRecovery,
NSOpenGLPFAColorSize, 32,
NSOpenGLPFAAllowOfflineRenderers, /* Allow use of offline renderers */
0
};
pf = [[NSOpenGLPixelFormat alloc] initWithAttributes:(void *)&attr];
}
return pf;
}
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
- (void)setContextOptions:(NSDictionary *)dict
{
_contextOptions = dict;
self.context = nil;
}
- (void)setImage:(CIImage *)image
{
[self setImage:image dirtyRect:CGRectInfinite];
}
- (void)setImage:(CIImage *)image dirtyRect:(CGRect)rect
{
if (_image != image)
{
_image = image;
if (CGRectIsInfinite(rect)) {
[self setNeedsDisplay:YES];
}
else {
[self setNeedsDisplayInRect:NSRectFromCGRect(rect)];
}
}
}
- (void)prepareOpenGL
{
GLint parm = 1;
/* Enable beam-synced updates. */
[[self openGLContext] setValues:&parm forParameter:NSOpenGLCPSwapInterval];
/* Make sure that everything we don't need is disabled. Some of these
* are enabled by default and can slow down rendering. */
glDisable(GL_ALPHA_TEST);
glDisable(GL_DEPTH_TEST);
glDisable(GL_SCISSOR_TEST);
glDisable(GL_BLEND);
glDisable(GL_DITHER);
glDisable(GL_CULL_FACE);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask(GL_FALSE);
glStencilMask(0);
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glHint(GL_TRANSFORM_HINT_APPLE, GL_FASTEST);
}
- (void)viewBoundsDidChange:(NSRect)bounds
{
/* For subclasses. */
}
- (void)updateMatrices
{
NSRect bounds = [self bounds];
if (!NSEqualRects(bounds, _lastBounds)) {
[[self openGLContext] update];
/* Install an orthographic projection matrix (no perspective)
* with the origin in the bottom left and one unit equal to one
* device pixel. */
glViewport(0, 0, bounds.size.width, bounds.size.height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, bounds.size.width, 0, bounds.size.height, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
_lastBounds = bounds;
[self viewBoundsDidChange:bounds];
}
}
- (BOOL)displaysWhenScreenProfileChanges
{
return YES;
}
- (void)viewWillMoveToWindow:(NSWindow*)newWindow
{
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center removeObserver:self name:NSWindowDidChangeScreenProfileNotification object:nil];
[center addObserver:self selector:@selector(displayProfileChanged:) name:NSWindowDidChangeScreenProfileNotification object:newWindow];
[center addObserver:self selector:@selector(displayProfileChanged:) name:NSWindowDidMoveNotification object:newWindow];
// When using OpenGL, we should disable the window's "one-shot" feature
[newWindow setOneShot:NO];
}
- (void)displayProfileChanged:(NSNotification*)notification
{
CGDirectDisplayID oldDid = _directDisplayID;
_directDisplayID = (CGDirectDisplayID)[[[[[self window] screen] deviceDescription] objectForKey:@"NSScreenNumber"] pointerValue];
if (_directDisplayID == oldDid) {
return;
}
_cglContext = [[self openGLContext] CGLContextObj];
if (pixelFormat == nil)
{
pixelFormat = [self pixelFormat];
if (pixelFormat == nil) {
pixelFormat = [[self class] defaultPixelFormat];
}
}
CGLLockContext(_cglContext);
{
// Create a new CIContext using the new output color space
// Since the cgl context will be rendered to the display, it is valid to rely on CI to get the colorspace from the context.
self.context = [CIContext contextWithCGLContext:_cglContext pixelFormat:[pixelFormat CGLPixelFormatObj] colorSpace:nil options:_contextOptions];
}
CGLUnlockContext(_cglContext);
}
- (void)drawRect:(NSRect)rect
{
[[self openGLContext] makeCurrentContext];
/* Allocate a CoreImage rendering context using the view's OpenGL
* context as its destination if none already exists. */
if (self.context == nil) {
[self displayProfileChanged:nil];
}
CGRect integralRect = CGRectIntegral(NSMakeRect(0, 0, 5184, 3456));
if ([NSGraphicsContext currentContextDrawingToScreen])
{
[self updateMatrices];
/*
Clear the specified subrect of the OpenGL surface then render the image into the view. Use the GL scissor test to clip to the subrect. Ask CoreImage to generate an extra pixel in case it has to interpolate (allow for hardware inaccuracies).
*/
CGRect rr = CGRectIntersection(CGRectInset (integralRect, -1.0f, -1.0f), NSRectToCGRect(_lastBounds));
glScissor(integralRect.origin.x, integralRect.origin.y, integralRect.size.width, integralRect.size.height);
glEnable(GL_SCISSOR_TEST);
glClear(GL_COLOR_BUFFER_BIT);
if ([self respondsToSelector:@selector(drawRect:inCIContext:)]) {
// For Subclasses to provide their own drawing method.
[(id <SampleCIViewDraw>)self drawRect:NSRectFromCGRect(rr) inCIContext:self.context];
}
else {
if (self.image != nil) {
[self.context drawImage:self.image inRect:rr fromRect:rr];
}
}
glDisable(GL_SCISSOR_TEST);
/*
Flush the OpenGL command stream. If the view is double buffered this should be replaced by [[self openGLContext] flushBuffer].
*/
glFlush();
}
else
{
/* Printing the view contents. Render using CG, not OpenGL. */
if ([self respondsToSelector:@selector (drawRect:inCIContext:)]) {
[(id <SampleCIViewDraw>)self drawRect:NSRectFromCGRect(integralRect) inCIContext:self.context];
}
else {
if (self.image != nil) {
CGImageRef cgImage = [self.context createCGImage:self.image fromRect:integralRect format:kCIFormatRGBA16 colorSpace:nil];
if (cgImage != NULL) {
CGContextDrawImage([[NSGraphicsContext currentContext] graphicsPort], integralRect, cgImage);
CGImageRelease(cgImage);
}
}
}
}
}
@end
我遇到的问题是我的图片尺寸为5184x3456px，但我的视图尺寸为800x600。如何在我的视图中显示我的图像。一直试图理解代码，但无处可去。
尝试使用glScalef（0.8,0.8,0.8）;但它做了什么，它缩放了显示在屏幕上的部分。
答案 0 :(得分：0)
事实证明我画的是错误的。
了解一下，解决了这个问题。
[self.context drawImage:self.image inRect:rr fromRect: imageRect];