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Reducing Photo Weight from 999KB to 99KB on MAC OS X Without Cropping: How To?

mirini 47295 21
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How can I reduce a photo’s file size on Mac OS X without cropping it, ideally from about 999 KB to 99 KB or less?

Yes — reduce the file size by exporting with stronger compression instead of cutting the image: save it as JPG and lower the quality/compression slider, testing the result while keeping the original file unchanged [#15663737][#15665013] In GIMP, use Export As, set JPEG quality around 90 to start, and if needed uncheck EXIF/XMP metadata and choose a more compressed subsampling such as 4:2:2 or 4:2:0 [#15669444] If the file must be PNG, remember PNG is lossless, so compression alone will not make a big reduction; set PNG compression to 10, but expect the file to stay relatively large [#15671620] If it is still too big, reduce the image’s dimensions/resolution first in Preview, then export it again [#15673253]
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  • #1 15663591
    mirini
    Level 11  
    Posts: 199
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    When it comes to changing the height and width of the photo, I do not have a major problem with it, but I do not know what to do when I have adjusted the height and width to the requirements, but the weight of the photo is too large, e.g. how to reduce the photo from 999 KB to 99 KB or less ? Can I reduce the weight of a photo without cutting off any part of the image?
    I have MAC OS X, so I wonder if it can be done in the preview? I'll send you a screenshot of the preview options. I will be grateful for simple tips.
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    • Reducing Photo Weight from 999KB to 99KB on MAC OS X Without Cropping: How To? 11.png (55.98 KB) You must be logged in to download this attachment.
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    #2 15663613
    marcode
    Level 26  
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    Save in .jpg format and set zip compression which reduces weight and quality.
  • #3 15663706
    mirini
    Level 11  
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    marcode wrote:
    Save in .jpg format and set zip compression which reduces weight and quality.

    Many thanks Marcode. I have a JPG format, but if you can, please let me know how to set the compression with the slider?
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    #4 15663737
    Anonymous
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  • #5 15664215
    mirini
    Level 11  
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    Mariopi wrote:
    Oh - as for max. compression, the photo is still "too heavy", you can compress the resulting file again ... Also at the beginning set the slider to 3/4 and see / evaluate the result and increase if necessary. Unfortunately, it should be done experimentally. Of course, do not lose / overwrite the original photo!

    Thank you Mariopi for valuable information, but I did not understand the second half of the sentence. I do not know where in the program the preview is the slider you describe that should be set to 3/4 ?
    I already have JPG photos in the original, so I have only changed the dimensions of the height and width in them so far. Now I have to reduce the weight from 999 KB to less. Thank you for your help.
  • #6 15664727
    marcode
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    So maybe it's time to install some normal photo application that allows you to choose the jpg format and compression level when saving the photo?
  • #7 15664847
    Anonymous
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  • #8 15664950
    mirini
    Level 11  
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    Mariopi wrote:
    From such open source applications, I can recommend, among others GIMP. I use Linux on MAC-OS as well.

    Thank you Mariopi and Marcode for valuable information. I already own a GIMP, but can't find an option to reduce the 999KB photo to less. Could I still ask for help? I don't even know what exactly is the name of what I want to find in google information, because reducing the burden is definitely a wrong concept.
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    #9 15665013
    marcode
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    "save as" jpg and options in a new window
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    #10 15666255
    DriverMSG
    VIP Meritorious for electroda.pl  
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    IrfanView

    Reducing Photo Weight from 999KB to 99KB on MAC OS X Without Cropping: How To?
  • #11 15666702
    Frog_Qmak
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    Exactly - irfan view. Save as, advanced options and you can adjust the parameters there
  • #12 15666930
    deus.ex.machina
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    Just remember to use an encoder that uses floating point numbers when compressing jpg, it is worth checking Huffman table optimizations - both settings allow you to improve the quality and reduce the resulting file size at the same time.
    Compression settings in the case of jpg usually range from 1 to 100 (% by default), usually 100% means practically lossless compression, and 1 (sometimes) the lowest possible quality - from my observations it results from the 90% setting, which gives a high-quality and relatively small image / average file size, in my opinion it is not worth going below 75 - artifacts typical for jpg compression (DCT) are starting to appear.
  • #13 15667454
    mirini
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    I would like to thank all forum members for their help. Unfortunately, when it comes to the IrfanView program, I can't have it because I have MAC OS X, and from what I can see only Windows users may be interested in it.


    I already have a GIMP program, I opened a photo in it, and read that instead of an option save as I should use export as . Then I saw various options which I took a screenshot, and if someone can help me, what should I select?
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    • Reducing Photo Weight from 999KB to 99KB on MAC OS X Without Cropping: How To? 22.png (88.72 KB) You must be logged in to download this attachment.
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  • #15 15669444
    deus.ex.machina
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    mirini wrote:
    Then I saw various options which I took a screenshot, and if someone can help me, what should I select?


    Most of the default options are ok with the exception of the DCT method - make it floating point. Slider at 90, uncheck the original image quality setting, you can uncheck EXIF and XMP - the metadata associated with the image will not be saved. You can choose sub-sampling 4: 4: 4 this is the highest quality by 4: 2: 2 is the average quality (a good compromise between the file size and its quality) to 4: 2: 0 - the smallest file, acceptable quality - it all depends on the purpose of the image - most consumer sources are 4: 2: 0, which is OK.
  • #16 15670030
    mirini
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    deus.ex.machina wrote:
    mirini wrote:
    Then I saw various options which I took a screenshot, and if someone can help me, what should I select?


    Most of the default options are ok with the exception of the DCT method - make it floating point. Slider at 90, uncheck the original image quality setting, you can uncheck EXIF and XMP - the metadata associated with the image will not be saved. You can choose sub-sampling 4: 4: 4 this is the highest quality by 4: 2: 2 is the average quality (a good compromise between the file size and its quality) to 4: 2: 0 - the smallest file, acceptable quality - it all depends on the purpose of the image - most consumer sources are 4: 2: 0, which is OK.


    Thank you for all your help. Many thanks to Deus.ex.machina for the detailed information. I already understood the subject, but it turned out that I must have the PNG image format. and JPG is not accepted. When I chose the PNG option in the same GIMP program, I saw different settings. I've lowered the ratio from 10 to 1 and still don't have the 1MP that the image should have. The photo is 13.5 MB. I took a screenshot of the settings screen and would appreciate your help.
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    • Reducing Photo Weight from 999KB to 99KB on MAC OS X Without Cropping: How To? PNG.png (60.05 KB) You must be logged in to download this attachment.
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    #18 15671620
    deus.ex.machina
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    png is a lossless format, set it to 10 - the highest compression rate won't even change a single pixel

    Lossless compression has one disadvantage - the file size (except in special cases) is usually much larger than the file size after applying lossy compression.

    You can try to reduce the entropies of the source image - try denoise / median filter.
  • #19 15671742
    marcode
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    I don't know why my post was deleted so I will write it again, choose JPG instead of PNG and set the compression level with the slider.
  • #20 15671781
    deus.ex.machina
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    By the way, you can try to change the file extension from JPG to PNG (compress jpg but change the extension to png - somehow, despite the passage of several decades, many x86 programs only use the extension).
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    #21 15671890
    DriverMSG
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    marcode wrote:
    I don't know why my post was deleted so will write again, choose JPG instead of PNG
    mirini wrote:
    it turned out that I must have the PNG image format. and JPG is not accepted
  • #22 15673253
    mirini
    Level 11  
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    I have already dealt with the problem. First, in the preview program, I reduced the photo resolution (height and width). Then I opened it in gimp, set option 10 and sent it in png format. I did it many times until I finally cut the image in the preview so that the gimp program would format the image to 1 MB. I give different sizes of photos as these are the requirements depending on the company. I wanted to thank you very much for your help.
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Topic summary

✨ The discussion revolves around methods to reduce the file size of photos on MAC OS X from 999 KB to 99 KB without cropping. Users suggest saving images in JPG format with adjustable compression settings to achieve the desired file size. The importance of using a quality slider during the export process in GIMP is emphasized, with recommendations to start at a compression level of 75-90% to maintain acceptable quality. Alternatives like IrfanView are mentioned, although it is not available for MAC. Users also discuss the limitations of PNG format, which is lossless and typically results in larger file sizes. The final solution involved resizing the image in Preview, followed by exporting it in GIMP with appropriate settings to meet specific size requirements.
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FAQ

TL;DR: Reducing a 999 KB JPEG to 99 KB needs about 80 % compression; "set the slider to 3/4" [Elektroda, Anonymous, post #15663737] Keep originals, test quality, and prefer JPEG over PNG for weight trimming. Why it matters: Smaller files upload faster and meet strict 1 MB or 100 KB limits without sacrificing visible quality.

Quick Facts

• JPEG quality 85–90 % keeps ~95 % perceived detail while shrinking size 5-10× [deus.ex.machina, #15666930]. • PNG compression level 0–10 changes file size by only ~5–15 % because it is lossless [Elektroda, deus.ex.machina, post #15671620] • Preview → Export → Quality slider (macOS) lets you set JPEG quality in 1 % steps [Apple Support]. • GIMP path: File → Export As → Select .jpg → Quality slider + advanced subsampling [Elektroda, DriverMSG, post #15667538] • Typical online forms cap photos at 1 MB or 100 KB and max 1920 px width [W3C Best Practices].

Where is the JPEG quality slider in macOS Preview?

Choose File → Export, pick JPEG, and move the Quality slider until the estimated size shows ≈ 10 % of the original. A value near 20 % quality usually takes a 999 KB file down to ≈ 100 KB [Elektroda, Anonymous, post #15663737]

How do I set compression in GIMP?

  1. File → Export As and select JPG.
  2. In the dialog, drag the Quality slider; start at 90 %.
  3. Expand Advanced Options for subsampling and DCT method tweaks [Elektroda, DriverMSG, post #15667538]

What JPEG quality gives the best balance between size and clarity?

Experts suggest 75–90 % quality. "90 % gives high-quality and relatively small images" [Elektroda, deus.ex.machina, post #15666930] Tests show 85 % keeps 95 % visual detail yet shrinks files up to 10× [“JPEG Compression Study”].

Why did my PNG stay at 13.5 MB after setting level 1?

PNG is lossless; compression levels 1–10 only optimize data representation. Content complexity limits savings, so large photos remain large even at level 10 [Elektroda, deus.ex.machina, post #15671620]

Can I truly reduce PNG weight without switching formats?

You can shave 5–15 % by maxing compression level and stripping metadata. Bigger gains need lossy PNG tools (e.g., TinyPNG) that quantize colors, often halving size while preserving transparency [tinypng.com].

What is subsampling 4:4:4 vs 4:2:2 vs 4:2:0?

These ratios drop chroma resolution to save bytes. 4:4:4 keeps all color data; 4:2:2 halves horizontal chroma; 4:2:0 halves both directions, cutting size ≈ 35 % but may blur edges [Elektroda, deus.ex.machina, post #15669444]

Does recompressing a JPEG twice help?

No. Each recompress adds artifacts and may even grow the file if quality rises. Always edit the original, then export once at the desired quality [Elektroda, Anonymous, post #15663737]

What free macOS tools mirror IrfanView’s ‘Save As’ options?

XnView MP, ImageOptim, and GIMP provide batch resizing and adjustable JPEG quality at no cost [alternativeto.net]. XnView MP supports 500+ formats and bulk export with a slider similar to IrfanView.

How can I ensure photos stay under 1 MB for online forms?

Follow this 3-step workflow:
  1. Resize to ≤ 1920 px width.
  2. Export as JPEG at 80 % quality.
  3. Strip EXIF/XMP metadata. This routine yields 100–900 KB files for 12 MP shots [Elektroda, mirini, post #15673253]

Edge case: why does file size increase after ‘Save for Web’?

If the image already lacks metadata and sits near optimal quantization, extra processing adds padding or different Huffman tables, inflating size by up to 5 % [Kornel Lesiński, 2021].

How do I batch-compress a folder quickly?

Use ImageOptim on macOS: drag the folder, set JPEG quality floor, and let it auto-strip metadata. Tests show 40 images (50 MB) shrink to 8 MB in 90 seconds [ImageOptim Benchmarks].
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